Records |
Author |
Lavor, I.R.; da Costa, D.R.; Covaci, L.; Milošević, M.V.; Peeters, F.M.; Chaves, A. |
Title |
Zitterbewegung of moiré excitons in twisted MoS₂/WSe₂ heterobilayers |
Type |
A1 Journal article |
Year |
2021 |
Publication |
Physical review letters |
Abbreviated Journal |
|
Volume |
127 |
Issue |
10 |
Pages |
106801 |
Keywords |
A1 Journal article; Electron microscopy for materials research (EMAT); Condensed Matter Theory (CMT) |
Abstract |
The moire pattern observed in stacked noncommensurate crystal lattices, such as heterobilayers of transition metal dichalcogenides, produces a periodic modulation of their band gap. Excitons subjected to this potential landscape exhibit a band structure that gives rise to a quasiparticle dubbed the moire exciton. In the case of MoS2/WSe2 heterobilayers, the moire trapping potential has honeycomb symmetry and, consequently, the moire exciton band structure is the same as that of a Dirac-Weyl fermion, whose mass can be further tuned down to zero with a perpendicularly applied field. Here we show that, analogously to other Dirac-like particles, the moire exciton exhibits a trembling motion, also known as Zitterbewegung, whose long timescales are compatible with current experimental techniques for exciton dynamics. This promotes the study of the dynamics of moire excitons in van der Waals heterostructures as an advantageous solid-state platform to probe Zitterbewegung, broadly tunable by gating and interlayer twist angle. |
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Corporate Author |
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Place of Publication |
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Language |
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Wos |
000692200800020 |
Publication Date |
2021-08-31 |
Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
1079-7114 |
ISBN |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
Impact Factor |
|
Times cited |
5 |
Open Access |
OpenAccess |
Notes |
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Approved |
Most recent IF: NA |
Call Number |
UA @ admin @ c:irua:181599 |
Serial |
6896 |
Permanent link to this record |
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Author |
da Costa, D.R.; Chaves, A.; Farias, G.A.; Covaci, L.; Peeters, F.M. |
Title |
Wave-packet scattering on graphene edges in the presence of a pseudomagnetic field |
Type |
A1 Journal article |
Year |
2012 |
Publication |
Physical review : B : condensed matter and materials physics |
Abbreviated Journal |
Phys Rev B |
Volume |
86 |
Issue |
11 |
Pages |
115434 |
Keywords |
A1 Journal article; Condensed Matter Theory (CMT) |
Abstract |
The scattering of a Gaussian wave packet in armchair and zigzag graphene edges is theoretically investigated by numerically solving the time-dependent Schrodinger equation for the tight-binding model Hamiltonian. Our theory allows us to investigate scattering in reciprocal space, and depending on the type of graphene edge we observe scattering within the same valley, or between different valleys. In the presence of an external magnetic field, the well-known skipping orbits are observed. However, our results demonstrate that in the case of a pseudomagnetic field, induced by nonuniform strain, the scattering by an armchair edge results in a nonpropagating edge state. |
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Corporate Author |
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Thesis |
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Publisher |
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Place of Publication |
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Editor |
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Language |
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Wos |
000309174100005 |
Publication Date |
2012-09-21 |
Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
1098-0121;1550-235X; |
ISBN |
|
Additional Links |
UA library record; WoS full record; WoS citing articles |
Impact Factor |
3.836 |
Times cited |
28 |
Open Access |
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Notes |
; Discussions with E. B. Barros are gratefully acknowledged. This work was supported by the Brazilian Council for Research (CNPq), the Flemish Science Foundation (FWO-Vl), the ESF-EuroGRAPHENE (project CONGRAN), and the bilateral program between Flanders and Brazil. ; |
Approved |
Most recent IF: 3.836; 2012 IF: 3.767 |
Call Number |
UA @ lucian @ c:irua:101833 |
Serial |
3907 |
Permanent link to this record |
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Author |
Linard, F.J.A.; Moura, V.N.; Covaci, L.; Milošević, M.V.; Chaves, A. |
Title |
Wave-packet scattering at a normal-superconductor interface in two-dimensional materials : a generalized theoretical approach |
Type |
A1 Journal article |
Year |
2023 |
Publication |
Physical review B |
Abbreviated Journal |
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Volume |
107 |
Issue |
16 |
Pages |
165306-165309 |
Keywords |
A1 Journal article; Electron microscopy for materials research (EMAT); Condensed Matter Theory (CMT) |
Abstract |
A wave-packet time evolution method, based on the split-operator technique, is developed to investigate the scattering of quasiparticles at a normal-superconductor interface of arbitrary profile and shape. As a practical application, we consider a system where low-energy electrons can be described as Dirac particles, which is the case for most two-dimensional materials, such as graphene and transition-metal dichalcogenides. However, the method is easily adapted for other cases such as electrons in few-layer black phosphorus or any Schrodinger quasiparticles within the effective mass approximation in semiconductors. We employ the method to revisit Andreev reflection in mono-, bi-, and trilayer graphene, where specular-and retro-reflection cases are observed for electrons scattered by a steplike superconducting region. The effect of opening a zero-gap channel across the superconducting region on the electron and hole scattering is also addressed, as an example of the versatility of the technique proposed here. |
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Corporate Author |
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Thesis |
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Publisher |
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Place of Publication |
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Editor |
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Language |
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Wos |
000974675700006 |
Publication Date |
2023-04-14 |
Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
2469-9969; 2469-9950 |
ISBN |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
Impact Factor |
3.7 |
Times cited |
|
Open Access |
OpenAccess |
Notes |
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Approved |
Most recent IF: 3.7; 2023 IF: 3.836 |
Call Number |
UA @ admin @ c:irua:196709 |
Serial |
8954 |
Permanent link to this record |
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Author |
Chaves, A.; Covaci, L.; Rakhimov, K.Y.; Farias, G.A.; Peeters, F.M. |
Title |
Wave-packet dynamics and valley filter in strained graphene |
Type |
A1 Journal article |
Year |
2010 |
Publication |
Physical review : B : condensed matter and materials physics |
Abbreviated Journal |
Phys Rev B |
Volume |
82 |
Issue |
20 |
Pages |
205430 |
Keywords |
A1 Journal article; Condensed Matter Theory (CMT) |
Abstract |
The time evolution of a wave packet in strained graphene is studied within the tight-binding model and continuum model. The effect of an external magnetic field, as well as a strain-induced pseudomagnetic field, on the wave-packet trajectories and zitterbewegung are analyzed. Combining the effects of strain with those of an external magnetic field produces an effective magnetic field which is large in one of the Dirac cones, but can be practically zero in the other. We construct an efficient valley filter, where for a propagating incoming wave packet consisting of momenta around the K and K' Dirac points, the outgoing wave packet exhibits momenta in only one of these Dirac points while the components of the packet that belong to the other Dirac point are reflected due to the Lorentz force. We also found that the zitterbewegung is permanent in time in the presence of either external or strain-induced magnetic fields, but when both the external and strain-induced magnetic fields are present, the zitterbewegung is transient in one of the Dirac cones, whereas in the other cone the wave packet exhibits permanent spatial oscillations. |
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Corporate Author |
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Thesis |
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Publisher |
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Place of Publication |
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Editor |
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Language |
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Wos |
000284401600007 |
Publication Date |
2010-11-19 |
Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
1098-0121;1550-235X; |
ISBN |
|
Additional Links |
UA library record; WoS full record; WoS citing articles |
Impact Factor |
3.836 |
Times cited |
95 |
Open Access |
|
Notes |
; This work was financially supported by CNPq under NanoBioEstruturas Contract No. 555183/2005-0, PRONEX/CNPq/FUNCAP, CAPES, the Bilateral program between Flanders and Brazil, the Belgian Science Policy (IAP), and the Flemish Science Foundation (FWO-V1) ; |
Approved |
Most recent IF: 3.836; 2010 IF: 3.774 |
Call Number |
UA @ lucian @ c:irua:95542 |
Serial |
3905 |
Permanent link to this record |
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Author |
Zhang, L.-F.; Covaci, L.; Milošević, M.V.; Berdiyorov, G.R.; Peeters, F.M. |
Title |
Vortex states in nanoscale superconducting squares : the influence of quantum confinement |
Type |
A1 Journal article |
Year |
2013 |
Publication |
Physical review : B : condensed matter and materials physics |
Abbreviated Journal |
Phys Rev B |
Volume |
88 |
Issue |
14 |
Pages |
144501 |
Keywords |
A1 Journal article; Condensed Matter Theory (CMT) |
Abstract |
Bogoliubov-de Gennes theory is used to investigate the effect of the size of a superconducting square on the vortex states in the quantum confinement regime. When the superconducting coherence length is comparable to the Fermi wavelength, the shape resonances of the superconducting order parameter have strong influence on the vortex configuration. Several unconventional vortex states, including asymmetric ones, giant-multivortex combinations, and states comprising giant antivortices, were found as ground states and their stability was found to be very sensitive on the value of k(F)xi(0), the size of the sample W, and the magnetic flux Phi. By increasing the temperature and/or enlarging the size of the sample, quantum confinement is suppressed and the conventional mesoscopic vortex states as predicted by the Ginzburg-Laudau (GL) theory are recovered. However, contrary to the GL results we found that the states containing symmetry-induced vortex-antivortex pairs are stable over the whole temperature range. It turns out that the inhomogeneous order parameter induced by quantum confinement favors vortex-antivortex molecules, as well as giant vortices with a rich structure in the vortex core-unattainable in the GL domain. |
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Corporate Author |
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Thesis |
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Publisher |
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Place of Publication |
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Editor |
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Language |
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Wos |
000325498300004 |
Publication Date |
2013-10-09 |
Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
1098-0121;1550-235X; |
ISBN |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
Impact Factor |
3.836 |
Times cited |
19 |
Open Access |
|
Notes |
; This work was supported by the Flemish Science Foundation (FWO-Vlaanderen) and Methusalem Funding of the Flemish government. ; |
Approved |
Most recent IF: 3.836; 2013 IF: 3.664 |
Call Number |
UA @ lucian @ c:irua:111145 |
Serial |
3891 |
Permanent link to this record |
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Author |
Richardson, C.L.; Edkins, S.D.; Berdiyorov, G.R.; Chua, C.J.; Griffiths, J.P.; Jones, G.A.C.; Buitelaar, M.R.; Narayan, V.; Sfigakis, F.; Smith, C.G.; Covaci, L.; Connolly, M.R.; |
Title |
Vortex detection and quantum transport in mesoscopic graphene Josephson-junction arrays |
Type |
A1 Journal article |
Year |
2015 |
Publication |
Physical review : B : condensed matter and materials physics |
Abbreviated Journal |
Phys Rev B |
Volume |
91 |
Issue |
91 |
Pages |
245418 |
Keywords |
A1 Journal article; Condensed Matter Theory (CMT) |
Abstract |
We investigate mesoscopic Josephson-junction arrays created by patterning superconducting disks on monolayer graphene, concentrating on the high-T/T-c regime of these devices and the phenomena which contribute to the superconducting glass state in diffusive arrays. We observe features in the magnetoconductance at rational fractions of flux quanta per array unit cell, which we attribute to the formation of flux-quantized vortices. The applied fields at which the features occur are well described by Ginzburg-Landau simulations that take into account the number of unit cells in the array. We find that the mean conductance and universal conductance fluctuations are both enhanced below the critical temperature and field of the superconductor, with greater enhancement away from the graphene Dirac point. |
Address |
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Corporate Author |
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Thesis |
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Publisher |
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Place of Publication |
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Editor |
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Language |
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Wos |
000356129800012 |
Publication Date |
2015-06-15 |
Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
1098-0121;1550-235X; |
ISBN |
|
Additional Links |
UA library record; WoS full record; WoS citing articles |
Impact Factor |
3.836 |
Times cited |
2 |
Open Access |
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Notes |
; This work was financially supported by the Engineering and Physical Sciences Research Council, and an NPL/EPSRC Joint Postdoctoral Partnership. Supporting data for this paper is available at the DSpace@Cambridge data repository (https://www.repository.cam.ac.uk/handle/1810/248242). ; |
Approved |
Most recent IF: 3.836; 2015 IF: 3.736 |
Call Number |
c:irua:126982 |
Serial |
3865 |
Permanent link to this record |
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Author |
Dell'Anna, L.; Perali, A.; Covaci, L.; Neilson, D. |
Title |
Using magnetic stripes to stabilize superfluidity in electron-hole double monolayer graphene |
Type |
A1 Journal article |
Year |
2015 |
Publication |
Physical review : B : condensed matter and materials physics |
Abbreviated Journal |
Phys Rev B |
Volume |
92 |
Issue |
92 |
Pages |
220502 |
Keywords |
A1 Journal article; Condensed Matter Theory (CMT) |
Abstract |
Experiments have confirmed that double monolayer graphene does not generate finite-temperature electron-hole superfluidity, because of very strong screening of the pairing attraction. The linear dispersing energy bands in monolayer graphene block any attempt to reduce the strength of the screening. We propose a hybrid device with two sheets of monolayer graphene in a modulated periodic perpendicular magnetic field. The field preserves the isotropic Dirac cones of the original monolayers but reduces the slope of the cones, making the monolayer Fermi velocity v(F) smaller. We demonstrate that with current experimental techniques, the reduction in vF can weaken the screening sufficiently to allow electron-hole superfluidity at measurable temperatures. |
Address |
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Corporate Author |
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Thesis |
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Publisher |
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Place of Publication |
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Editor |
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Language |
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Wos |
000366500100004 |
Publication Date |
2015-12-14 |
Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
1098-0121 |
ISBN |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
Impact Factor |
3.836 |
Times cited |
7 |
Open Access |
|
Notes |
; We thank M. Zarenia for useful discussions. L.D. acknowledges financial support from MIUR: FIRB 2012, Grant No. RBFR12NLNA_002, and PRIN, Grant No. 2010LLKJBX. A.P. and D.N. acknowledge financial support from University of Camerino FAR project CESEMN. L.C. acknowledges financial support from Flemish Science Foundation (FWO). ; |
Approved |
Most recent IF: 3.836; 2015 IF: 3.736 |
Call Number |
c:irua:130211 |
Serial |
4069 |
Permanent link to this record |
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Author |
Zhang, L.-F.; Covaci, L.; Milošević, M.V.; Berdiyorov, G.R.; Peeters, F.M. |
Title |
Unconventional vortex states in nanoscale superconductors due to shape-induced resonances in the inhomogeneous Cooper-pair condensate |
Type |
A1 Journal article |
Year |
2012 |
Publication |
Physical review letters |
Abbreviated Journal |
Phys Rev Lett |
Volume |
109 |
Issue |
10 |
Pages |
107001 |
Keywords |
A1 Journal article; Condensed Matter Theory (CMT) |
Abstract |
Vortex matter in mesoscopic superconductors is known to be strongly affected by the geometry of the sample. Here we show that in nanoscale superconductors with coherence length comparable to the Fermi wavelength the shape resonances of the order parameter results in an additional contribution to the quantum topological confinement-leading to unconventional vortex configurations. Our Bogoliubov-de Gennes calculations in a square geometry reveal a plethora of asymmetric, giant multivortex, and vortex-antivortex structures, stable over a wide range of parameters and which are very different from those predicted by the Ginzburg-Landau theory. These unconventional states are relevant for high-T-c nanograins, confined Bose-Einstein condensates, and graphene flakes with proximity-induced superconductivity. |
Address |
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Corporate Author |
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Thesis |
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Publisher |
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Place of Publication |
New York, N.Y. |
Editor |
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Language |
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Wos |
000308295700014 |
Publication Date |
2012-09-05 |
Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
0031-9007;1079-7114; |
ISBN |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
Impact Factor |
8.462 |
Times cited |
31 |
Open Access |
|
Notes |
; This work was supported by the Flemish Science Foundation (FWO-Vlaanderen). ; |
Approved |
Most recent IF: 8.462; 2012 IF: 7.943 |
Call Number |
UA @ lucian @ c:irua:101850 |
Serial |
3801 |
Permanent link to this record |
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Author |
Pandey, T.; Covaci, L.; Peeters, F.M. |
Title |
Tuning flexoelectricty and electronic properties of zig-zag graphene nanoribbons by functionalization |
Type |
A1 Journal article |
Year |
2021 |
Publication |
Carbon |
Abbreviated Journal |
Carbon |
Volume |
171 |
Issue |
|
Pages |
551-559 |
Keywords |
A1 Journal article; Electron microscopy for materials research (EMAT); Condensed Matter Theory (CMT) |
Abstract |
The flexoelectric and electronic properties of zig-zag graphene nanoribbons are explored under mechanical bending using state of the art first principles calculations. A linear dependence of the bending induced out of plane polarization on the applied strain gradient is found. The inferior flexoelectric properties of graphene nanoribbons can be improved by more than two orders of magnitude by hydrogen and fluorine functionalization (CH and CF nanoribbons). A large out of plane flexoelectric effect is predicted for CF nanoribbons. The origin of this enhancement lies in the electro-negativity difference between carbon and fluorine atoms, which breaks the out of plane charge symmetry even for a small strain gradient. The flexoelectric effect can be further improved by co-functionalization with hydrogen and fluorine (CHF Janus-type nanoribbon), where a spontaneous out of plane dipole moment is formed even for flat nanoribbons. We also find that bending can control the charge localization of valence band maxima and therefore enables the tuning of the hole effective masses and band gaps. These results present an important advance towards the understanding of flexoelectric and electronic properties of hydrogen and fluorine functionalized graphene nanoribbons, which can have important implications for flexible electronic applications. (C) 2020 Elsevier Ltd. All rights reserved. |
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Corporate Author |
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Thesis |
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Publisher |
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Place of Publication |
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Editor |
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Language |
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Wos |
000598371500058 |
Publication Date |
2020-09-17 |
Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
0008-6223 |
ISBN |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
Impact Factor |
6.337 |
Times cited |
15 |
Open Access |
OpenAccess |
Notes |
; The computational resources and services used for the first-principles calculations in this work were provided by the VSC (Flemish Supercomputer Center), funded by the Flemish Science Foundation (FWO-VI). T. P. is supported by a postdoctoral research fellowship from BOF-UAntwerpen. ; |
Approved |
Most recent IF: 6.337 |
Call Number |
UA @ admin @ c:irua:175014 |
Serial |
6700 |
Permanent link to this record |
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Author |
Chaves, A.; Moura, V.N.; Linard, F.J.A.; Covaci, L.; Milošević, M.V. |
Title |
Tunable magnetic focusing using Andreev scattering in superconductor-graphene hybrid devices |
Type |
A1 Journal article |
Year |
2020 |
Publication |
Journal Of Applied Physics |
Abbreviated Journal |
J Appl Phys |
Volume |
128 |
Issue |
12 |
Pages |
124303 |
Keywords |
A1 Journal article; Electron microscopy for materials research (EMAT); Condensed Matter Theory (CMT) |
Abstract |
We perform the wavepacket dynamics simulation of a graphene-based device where propagating electron trajectories are tamed by an applied magnetic field toward a normal/superconductor interface. The magnetic field controls the incidence angle of the incoming electronic wavepacket at the interface, which results in the tunable electron-hole ratio in the reflected wave function due to the angular dependence of the Andreev reflection. Here, mapped control of the quasiparticle trajectories by the external magnetic field not only defines an experimental probe for fundamental studies of the Andreev reflection in graphene but also lays the foundation for further development of magnetic focusing devices based on nanoengineered superconducting two-dimensional materials. |
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Corporate Author |
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Thesis |
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Publisher |
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Place of Publication |
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Editor |
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Language |
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Wos |
000576393200002 |
Publication Date |
2020-09-28 |
Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
0021-8979; 1089-7550 |
ISBN |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
Impact Factor |
3.2 |
Times cited |
1 |
Open Access |
Not_Open_Access |
Notes |
; This work was supported by the Brazilian Council for Research (CNPq) through the PRONEX/FUNCAP and PQ programs and by the Research Foundation-Flanders (FWO). ; |
Approved |
Most recent IF: 3.2; 2020 IF: 2.068 |
Call Number |
UA @ admin @ c:irua:172730 |
Serial |
6639 |
Permanent link to this record |
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Author |
Chaves, A.; Covaci, L.; Peeters, F.M.; Milošević, M.V. |
Title |
Topologically protected moiré exciton at a twist-boundary in a van der Waals heterostructure |
Type |
A1 Journal article |
Year |
2022 |
Publication |
2D materials |
Abbreviated Journal |
2D Mater |
Volume |
9 |
Issue |
2 |
Pages |
025012 |
Keywords |
A1 Journal article; Electron microscopy for materials research (EMAT); Condensed Matter Theory (CMT) |
Abstract |
A twin boundary in one of the layers of a twisted van der Waals heterostructure separates regions with near opposite inter-layer twist angles. In a MoS<sub>2</sub>/WSe<sub>2</sub>bilayer, the regions with<inline-formula><tex-math><?CDATA $Rh^h$?></tex-math><math overflow=“scroll”><msubsup><mi>R</mi><mi>h</mi><mi>h</mi></msubsup></math><inline-graphic href=“tdmac529dieqn1.gif” type=“simple” /></inline-formula>and<inline-formula><tex-math><?CDATA $Rh^X$?></tex-math><math overflow=“scroll”><msubsup><mi>R</mi><mi>h</mi><mi>X</mi></msubsup></math><inline-graphic href=“tdmac529dieqn2.gif” type=“simple” /></inline-formula>stacking registry that defined the sub-lattices of the moiré honeycomb pattern would be mirror-reflected across such a twist boundary. In that case, we demonstrate that topologically protected chiral moiré exciton states are confined at the twist boundary. These are one-dimensional and uni-directional excitons with opposite velocities for excitons composed by electronic states with opposite valley/spin character, enabling intrinsic, guided, and far reaching valley-polarized exciton currents. |
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Corporate Author |
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Thesis |
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Publisher |
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Place of Publication |
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Language |
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Wos |
000760518100001 |
Publication Date |
2022-04-01 |
Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
2053-1583 |
ISBN |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
Impact Factor |
5.5 |
Times cited |
3 |
Open Access |
OpenAccess |
Notes |
Fonds Wetenschappelijk Onderzoek; Conselho Nacional de Desenvolvimento Científico e Tecnológico, PQ ; |
Approved |
Most recent IF: 5.5 |
Call Number |
CMT @ cmt @c:irua:187124 |
Serial |
7046 |
Permanent link to this record |
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Author |
Zhang, L.-F.; Covaci, L.; Milošević, M.V. |
Title |
Topological phase transitions in small mesoscopic chiral p-wave superconductors |
Type |
A1 Journal article |
Year |
2017 |
Publication |
Physical review B |
Abbreviated Journal |
Phys Rev B |
Volume |
96 |
Issue |
22 |
Pages |
224512 |
Keywords |
A1 Journal article; Condensed Matter Theory (CMT) |
Abstract |
<script type='text/javascript'>document.write(unpmarked('Spin-triplet chiral p-wave superconductivity is typically described by a two-component order parameter, and as such is prone to unique emergent effects when compared to the standard single-component superconductors. Here we present the equilibrium phase diagram for small mesoscopic chiral p-wave superconducting disks in the presence of magnetic field, obtained by solving the microscopic Bogoliubov-de Gennes equations self-consistently. In the ultrasmall limit, the cylindrically symmetric giant-vortex states form the ground state of the system. However, with increasing sample size, the cylindrical symmetry is broken as the two components of the order parameter segregate into domains, and the number of fragmented domain walls between them characterizes the resulting states. Such domain walls are topological defects unique for the p-wave order, and constitute a dominant phase in the mesoscopic regime. Moreover, we find two possible types of domain walls, identified by their chirality-dependent interaction with the edge states.')); |
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Corporate Author |
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Thesis |
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Publisher |
American Physical Society |
Place of Publication |
New York, N.Y |
Editor |
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Language |
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Wos |
000418653500012 |
Publication Date |
2017-12-26 |
Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
|
Edition |
|
ISSN |
2469-9969; 2469-9950 |
ISBN |
|
Additional Links |
UA library record; WoS full record; WoS citing articles |
Impact Factor |
3.836 |
Times cited |
18 |
Open Access |
|
Notes |
; This work was supported by the Research Foundation Flanders (FWO-Vlaanderen) and the Special Research Funds of the University of Antwerp. ; |
Approved |
Most recent IF: 3.836 |
Call Number |
UA @ lucian @ c:irua:148504 |
Serial |
4901 |
Permanent link to this record |
|
|
|
Author |
Zhang, L.-F.; Covaci, L.; Peeters, F.M. |
Title |
Tomasch effect in nanoscale superconductors |
Type |
A1 Journal article |
Year |
2015 |
Publication |
Physical review : B : condensed matter and materials physics |
Abbreviated Journal |
Phys Rev B |
Volume |
91 |
Issue |
91 |
Pages |
024508 |
Keywords |
A1 Journal article; Condensed Matter Theory (CMT) |
Abstract |
The Tomasch effect (TE) is due to quasiparticle interference (QPI) as induced by a nonuniform superconducting order parameter, which results in oscillations in the density of states (DOS) at energies above the superconducting gap. Quantum confinement in nanoscale superconductors leads to an inhomogenerous distribution of the Cooperpair condensate, which, as we found, triggers the manifestation of a new TE. We investigate the electronic structure of nanoscale superconductors by solving the Bogoliubov-de Gennes (BdG) equations self-consistently and describe the TE determined by two types of processes, involving two-or three-subband QPIs. Both types of QPIs result in additional BCS-like Bogoliubov-quasiparticles and BCS-like energy gaps leading to oscillations in the DOS and modulated wave patterns in the local density of states. These effects are strongly related to the symmetries of the system. A reduced 4 x 4 inter-subband BdG Hamiltonian is established in order to describe analytically the TE of two-subband QPIs. Our study is relevant to nanoscale superconductors, either nanowires or thin films, Bose-Einsten condensates, and confined systems such as two-dimensional electron gas interface superconductivity. |
Address |
|
Corporate Author |
|
Thesis |
|
Publisher |
|
Place of Publication |
Lancaster, Pa |
Editor |
|
Language |
|
Wos |
000348473700003 |
Publication Date |
2015-01-16 |
Series Editor |
|
Series Title |
|
Abbreviated Series Title |
|
Series Volume |
|
Series Issue |
|
Edition |
|
ISSN |
1098-0121;1550-235X; |
ISBN |
|
Additional Links |
UA library record; WoS full record; WoS citing articles |
Impact Factor |
3.836 |
Times cited |
6 |
Open Access |
|
Notes |
; This work was supported by the Flemish Science Foundation (FWO-Vlaanderen) and the Methusalem funding of the Flemish Government. ; |
Approved |
Most recent IF: 3.836; 2015 IF: 3.736 |
Call Number |
c:irua:123864 |
Serial |
3670 |
Permanent link to this record |
|
|
|
Author |
de Sousa, J.S.; Covaci, L.; Peeters, F.M.; Farias, G.A. |
Title |
Time-dependent investigation of charge injection in a quantum dot containing one electron |
Type |
A1 Journal article |
Year |
2012 |
Publication |
Journal of applied physics |
Abbreviated Journal |
J Appl Phys |
Volume |
112 |
Issue |
9 |
Pages |
093705-93709 |
Keywords |
A1 Journal article; Condensed Matter Theory (CMT) |
Abstract |
The interaction of an injected electron towards a quantum dot (QD) containing a single confined electron is investigated using a flexible time-dependent quantum mechanics formalism, which allows both electrons to move and undergo quantum transitions. Different scenarios combining quantum dot dimensions, dielectric constant, injected wave packet energy, and width were explored, and our main results are: (i) due to the large characteristic transitions times between the confined state in the quantum dot and the delocalized state in the continuum, it is relatively difficult to ionize the occupied QD by Coulomb interaction solely and (ii) the charging state of the quantum dot can be sensed by direct injection of charges. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4759292] |
Address |
|
Corporate Author |
|
Thesis |
|
Publisher |
American Institute of Physics |
Place of Publication |
New York, N.Y. |
Editor |
|
Language |
|
Wos |
000311968400052 |
Publication Date |
2012-11-06 |
Series Editor |
|
Series Title |
|
Abbreviated Series Title |
|
Series Volume |
|
Series Issue |
|
Edition |
|
ISSN |
0021-8979; |
ISBN |
|
Additional Links |
UA library record; WoS full record; WoS citing articles |
Impact Factor |
2.068 |
Times cited |
1 |
Open Access |
|
Notes |
; This work was financially supported by the Brazilian National Research Council (CNPq), under Contract No. NanoBioEstruturas 555183/2005-0, Fundao Cearense de Apoio ao Desenvolvimento Cientfico e Tecnolgico (Funcap), CAPES, Pronex/CNPq/ Funcap, the Bilateral program between Flanders and Brazil, and the Flemish Science Foundation (FWO). ; |
Approved |
Most recent IF: 2.068; 2012 IF: 2.210 |
Call Number |
UA @ lucian @ c:irua:106014 |
Serial |
3664 |
Permanent link to this record |
|
|
|
Author |
Muñoz, W.A.; Covaci, L.; Peeters, F.M. |
Title |
Tight-binding study of bilayer graphene Josephson junctions |
Type |
A1 Journal article |
Year |
2012 |
Publication |
Physical review : B : condensed matter and materials physics |
Abbreviated Journal |
Phys Rev B |
Volume |
86 |
Issue |
18 |
Pages |
184505-184507 |
Keywords |
A1 Journal article; Condensed Matter Theory (CMT) |
Abstract |
Using highly efficient simulations of the tight-binding Bogoliubov-de-Gennes model, we solved self-consistently for the pair correlation and the Josephson current in a superconducting-bilayer graphene-superconducting Josephson junction. Different doping levels for the non-superconducting link are considered in the short- and long-junction regimes. Self-consistent results for the pair correlation and superconducting current resemble those reported previously for single-layer graphene except at the Dirac point, where remarkable differences in the proximity effect are found, as well as a suppression of the superconducting current in the long-junction regime. Inversion symmetry is broken by considering a potential difference between the layers and we found that the supercurrent can be switched if the junction length is larger than the Fermi length. |
Address |
|
Corporate Author |
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Thesis |
|
Publisher |
|
Place of Publication |
|
Editor |
|
Language |
|
Wos |
000310840400005 |
Publication Date |
2012-11-07 |
Series Editor |
|
Series Title |
|
Abbreviated Series Title |
|
Series Volume |
|
Series Issue |
|
Edition |
|
ISSN |
1098-0121;1550-235X; |
ISBN |
|
Additional Links |
UA library record; WoS full record; WoS citing articles |
Impact Factor |
3.836 |
Times cited |
13 |
Open Access |
|
Notes |
; This work was supported by the Flemish Science Foundation (FWO-VI). ; |
Approved |
Most recent IF: 3.836; 2012 IF: 3.767 |
Call Number |
UA @ lucian @ c:irua:105149 |
Serial |
3661 |
Permanent link to this record |
|
|
|
Author |
Muñoz, W.A.; Covaci, L.; Peeters, F.M. |
Title |
Tight-binding description of intrinsic superconducting correlations in multilayer graphene |
Type |
A1 Journal article |
Year |
2013 |
Publication |
Physical review : B : condensed matter and materials physics |
Abbreviated Journal |
Phys Rev B |
Volume |
87 |
Issue |
13 |
Pages |
134509-7 |
Keywords |
A1 Journal article; Condensed Matter Theory (CMT) |
Abstract |
Using highly efficient GPU-based simulations of the tight-binding Bogoliubov-de Gennes equations we solve self-consistently for the pair correlation in rhombohedral (ABC) and Bernal (ABA) multilayer graphene by considering a finite intrinsic s-wave pairing potential. We find that the two different stacking configurations have opposite bulk/surface behavior for the order parameter. Surface superconductivity is robust for ABC stacked multilayer graphene even at very low pairing potentials for which the bulk order parameter vanishes, in agreement with a recent analytical approach. In contrast, for Bernal stacked multilayer graphene, we find that the order parameter is always suppressed at the surface and that there exists a critical value for the pairing potential below which no superconducting order is achieved. We considered different doping scenarios and find that homogeneous doping strongly suppresses surface superconductivity while nonhomogeneous field-induced doping has a much weaker effect on the superconducting order parameter. For multilayer structures with hybrid stacking (ABC and ABA) we find that when the thickness of each region is small (few layers), high-temperature surface superconductivity survives throughout the bulk due to the proximity effect between ABC/ABA interfaces where the order parameter is enhanced. DOI: 10.1103/PhysRevB.87.134509 |
Address |
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Corporate Author |
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Thesis |
|
Publisher |
|
Place of Publication |
|
Editor |
|
Language |
|
Wos |
000317390000006 |
Publication Date |
2013-04-11 |
Series Editor |
|
Series Title |
|
Abbreviated Series Title |
|
Series Volume |
|
Series Issue |
|
Edition |
|
ISSN |
1098-0121;1550-235X; |
ISBN |
|
Additional Links |
UA library record; WoS full record; WoS citing articles |
Impact Factor |
3.836 |
Times cited |
37 |
Open Access |
|
Notes |
; This work was supported by the Flemish Science Foundation (FWO-Vl) and the Methusalem funding of the Flemish Government. ; |
Approved |
Most recent IF: 3.836; 2013 IF: 3.664 |
Call Number |
UA @ lucian @ c:irua:108469 |
Serial |
3660 |
Permanent link to this record |
|
|
|
Author |
Covaci, L.; Berciu, M. |
Title |
Survival of the Dirac points in rippled graphene |
Type |
A1 Journal article |
Year |
2008 |
Publication |
Physical Review Letters |
Abbreviated Journal |
Phys Rev Lett |
Volume |
100 |
Issue |
25 |
Pages |
256405 |
Keywords |
A1 Journal article; Electron Microscopy for Materials Science (EMAT); |
Abstract |
We study the effects of the rippling of a graphene sheet on quasiparticle dispersion. This is achieved using a generalization to the honeycomb lattice of the momentum average approximation, which is accurate for all coupling strengths and at all energies. We show that even though the position of the Dirac points may move and the Fermi speed can be renormalized significantly, quasiparticles with very long lifetimes survive near the Dirac points even for very strong couplings. |
Address |
Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia, Canada, V6T 1Z1 |
Corporate Author |
|
Thesis |
|
Publisher |
|
Place of Publication |
|
Editor |
|
Language |
English |
Wos |
000257230500047 |
Publication Date |
2008-06-26 |
Series Editor |
|
Series Title |
|
Abbreviated Series Title |
|
Series Volume |
|
Series Issue |
|
Edition |
|
ISSN |
0031-9007 |
ISBN |
|
Additional Links |
|
Impact Factor |
8.462 |
Times cited |
15 |
Open Access |
|
Notes |
|
Approved |
Most recent IF: 8.462; 2008 IF: 7.180 |
Call Number |
UA @ lucian @ |
Serial |
4010 |
Permanent link to this record |
|
|
|
Author |
Nasr Esfahani, D.; Covaci, L.; Peeters, F.M. |
Title |
Surface correlation effects in two-band strongly correlated slabs |
Type |
A1 Journal article |
Year |
2014 |
Publication |
Journal of physics : condensed matter |
Abbreviated Journal |
J Phys-Condens Mat |
Volume |
26 |
Issue |
7 |
Pages |
075601-75609 |
Keywords |
A1 Journal article; Condensed Matter Theory (CMT) |
Abstract |
Using an extension of the Gutzwiller approximation for an inhomogeneous system, we study the two-band Hubbard model with unequal band widths for a slab geometry. The aim is to investigate the mutual effect of individual bands on the spatial distribution of quasi-particle weight and charge density, especially near the surface of the slab. The main effect of the difference in band width is the presence of two different length scales corresponding to the quasi-particle profile of each band. This is enhanced in the vicinity of the critical interaction of the narrow band where an orbitally selective Mott transition occurs and a surface dead layer forms for the narrow band. For the doped case, two different regimes of charge transfer between the surface and the bulk of the slab are revealed. The charge transfer from surface/ center to center/ surface depends on both the doping level and the average relative charge accumulated in each band. Such effects could also be of importance when describing the accumulation of charges at the interface between structures made of multi-band strongly correlated materials. |
Address |
|
Corporate Author |
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Thesis |
|
Publisher |
|
Place of Publication |
London |
Editor |
|
Language |
|
Wos |
000330719500009 |
Publication Date |
2014-01-29 |
Series Editor |
|
Series Title |
|
Abbreviated Series Title |
|
Series Volume |
|
Series Issue |
|
Edition |
|
ISSN |
0953-8984;1361-648X; |
ISBN |
|
Additional Links |
UA library record; WoS full record; WoS citing articles |
Impact Factor |
2.649 |
Times cited |
1 |
Open Access |
|
Notes |
; This work was supported by the Flemish Science Foundation (FWO-Vl) and the Methusalem program of the Flemish government. One of us (LC) is a postdoctoral fellow of the FWO-Vl. ; |
Approved |
Most recent IF: 2.649; 2014 IF: 2.346 |
Call Number |
UA @ lucian @ c:irua:115723 |
Serial |
3395 |
Permanent link to this record |
|
|
|
Author |
Covaci, L.; Peeters, F.M. |
Title |
Superconducting proximity effect in graphene under inhomogeneous strain |
Type |
A1 Journal article |
Year |
2011 |
Publication |
Physical review : B : condensed matter and materials physics |
Abbreviated Journal |
Phys Rev B |
Volume |
84 |
Issue |
24 |
Pages |
241401-241401,4 |
Keywords |
A1 Journal article; Condensed Matter Theory (CMT) |
Abstract |
The interplay between quantum Hall states and Cooper pairs is usually hindered by the suppression of the superconducting state due to the strong magnetic fields needed to observe the quantum Hall effect. From this point of view, graphene is special since it allows the creation of strong pseudomagnetic fields due to strain. We show that in a Josephson junction made of strained graphene, Cooper pairs will diffuse into the strained region. The pair correlation function will be sublattice polarized due to the polarization of the local density of states in the zero pseudo-Landau level. We uncover two regimes: (1) one in which the cyclotron radius is larger than the junction length, in which case the supercurrent will be enhanced, and (2) the long junction regime where the supercurrent is strongly suppressed because the junction becomes an insulator. In the latter case quantized Hall states form and Andreev scattering at the normal/superconducting interface will induce edge states. Our numerical calculation has become possible due to an extension of the Chebyshev-Bogoliubovde Gennes method to computations on video cards (GPUs). |
Address |
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Corporate Author |
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Thesis |
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Publisher |
|
Place of Publication |
|
Editor |
|
Language |
|
Wos |
000297766600003 |
Publication Date |
2011-12-06 |
Series Editor |
|
Series Title |
|
Abbreviated Series Title |
|
Series Volume |
|
Series Issue |
|
Edition |
|
ISSN |
1098-0121;1550-235X; |
ISBN |
|
Additional Links |
UA library record; WoS full record; WoS citing articles |
Impact Factor |
3.836 |
Times cited |
27 |
Open Access |
|
Notes |
; This work was supported by the Flemish Science Foundation (FWO-Vl) and the Euro GRAPHENE project CONGRAN. Discussions with Andrey Chaves are gratefully acknowledged. ; |
Approved |
Most recent IF: 3.836; 2011 IF: 3.691 |
Call Number |
UA @ lucian @ c:irua:93962 |
Serial |
3364 |
Permanent link to this record |
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|
|
Author |
Flammia, L.; Zhang, L.-F.; Covaci, L.; Perali, A.; Milošević, M.V. |
Title |
Superconducting nanoribbon with a constriction : a quantum-confined Josephson junction |
Type |
A1 Journal article |
Year |
2018 |
Publication |
Physical review B |
Abbreviated Journal |
Phys Rev B |
Volume |
97 |
Issue |
13 |
Pages |
134514 |
Keywords |
A1 Journal article; Condensed Matter Theory (CMT) |
Abstract |
Extended defects are known to strongly affect nanoscale superconductors. Here, we report the properties of superconducting nanoribbons with a constriction formed between two adjacent step edges by solving the Bogoliubov-de Gennes equations self-consistently in the regime where quantum confinement is important. Since the quantum resonances of the superconducting gap in the constricted area are different from the rest of the nanoribbon, such constriction forms a quantum-confined S-S'-S Josephson junction, with a broadly tunable performance depending on the length and width of the constriction with respect to the nanoribbon, and possible gating. These findings provide an intriguing approach to further tailor superconducting quantum devices where Josephson effect is of use. |
Address |
|
Corporate Author |
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Thesis |
|
Publisher |
American Physical Society |
Place of Publication |
New York, N.Y |
Editor |
|
Language |
|
Wos |
000430161500004 |
Publication Date |
2018-04-17 |
Series Editor |
|
Series Title |
|
Abbreviated Series Title |
|
Series Volume |
|
Series Issue |
|
Edition |
|
ISSN |
2469-9969; 2469-9950 |
ISBN |
|
Additional Links |
UA library record; WoS full record; WoS citing articles |
Impact Factor |
3.836 |
Times cited |
7 |
Open Access |
|
Notes |
; This work was supported by the Research Foundation Flanders (FWO-Vlaanderen), the Special Research Funds of the University of Antwerp (TOPBOF), the Italian MIUR through the PRIN 2015 program (Contract No. 2015C5SEJJ001), the MultiSuper network, and the EU-COST NANOCOHYBRI action CA16218. ; |
Approved |
Most recent IF: 3.836 |
Call Number |
UA @ lucian @ c:irua:150754UA @ admin @ c:irua:150754 |
Serial |
4980 |
Permanent link to this record |
|
|
|
Author |
Muñoz, W.A.; Covaci, L.; Peeters, F.M. |
Title |
Superconducting current and proximity effect in ABA and ABC multilayer graphene Josephson junctions |
Type |
A1 Journal article |
Year |
2013 |
Publication |
Physical review : B : condensed matter and materials physics |
Abbreviated Journal |
Phys Rev B |
Volume |
88 |
Issue |
88 |
Pages |
214502 |
Keywords |
A1 Journal article; Condensed Matter Theory (CMT) |
Abstract |
Using a numerical tight-binding approach based on the Chebyshev–Bogoliubov–de Gennes method we describe Josephson junctions made of multilayer graphene contacted by top superconducting gates. Both Bernal (ABA) and rhombohedral (ABC) stacking are considered and we find that the type of stacking has a strong effect on the proximity effect and the supercurrent flow. For both cases the pair amplitude shows a polarization between dimer and nondimer atoms, being more pronounced for rhombohedral stacking. Even though the proximity effect in nondimer sites is enhanced when compared to single-layer graphene, we find that the supercurrent is suppressed. The spatial distribution of the supercurrent shows that for Bernal stacking the current flows only in the topmost layers while for rhombohedral stacking the current flows throughout the whole structure. |
Address |
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Corporate Author |
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Thesis |
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Publisher |
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Place of Publication |
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Editor |
|
Language |
|
Wos |
000328569900004 |
Publication Date |
2013-12-02 |
Series Editor |
|
Series Title |
|
Abbreviated Series Title |
|
Series Volume |
|
Series Issue |
|
Edition |
|
ISSN |
1098-0121;1550-235X; |
ISBN |
|
Additional Links |
UA library record; WoS full record; WoS citing articles |
Impact Factor |
3.836 |
Times cited |
4 |
Open Access |
|
Notes |
This work was supported by the Flemish Science Foundation (FWO-Vl) and the Methusalem funding of the Flemish Government |
Approved |
Most recent IF: 3.836; 2013 IF: 3.664 |
Call Number |
CMT @ cmt @ c:irua:128896 |
Serial |
3962 |
Permanent link to this record |
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|
|
Author |
Smeyers, R.; Milošević, M.V.; Covaci, L. |
Title |
Strong gate-tunability of flat bands in bilayer graphene due to moiré encapsulation between hBN monolayers |
Type |
A1 Journal article |
Year |
2023 |
Publication |
Nanoscale |
Abbreviated Journal |
|
Volume |
15 |
Issue |
9 |
Pages |
4561-4569 |
Keywords |
A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT); Condensed Matter Theory (CMT) |
Abstract |
When using hexagonal boron-nitride (hBN) as a substrate for graphene, the resulting moire pattern creates secondary Dirac points. By encapsulating a multilayer graphene within aligned hBN sheets the controlled moire stacking may offer even richer benefits. Using advanced tight-binding simulations on atomistically-relaxed heterostructures, here we show that the gap at the secondary Dirac point can be opened in selected moire-stacking configurations, and is independent of any additional vertical gating of the heterostructure. On the other hand, gating can broadly tune the gap at the principal Dirac point, and may thereby strongly compress the first moire mini-band in width against the moire-induced gap at the secondary Dirac point. We reveal that in hBN-encapsulated bilayer graphene this novel mechanism can lead to isolated bands flatter than 10 meV under moderate gating, hence presenting a convenient pathway towards electronically-controlled strongly-correlated states on demand. |
Address |
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Corporate Author |
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Thesis |
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Publisher |
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Place of Publication |
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Editor |
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Language |
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Wos |
000933052600001 |
Publication Date |
2023-02-07 |
Series Editor |
|
Series Title |
|
Abbreviated Series Title |
|
Series Volume |
|
Series Issue |
|
Edition |
|
ISSN |
2040-3364; 2040-3372 |
ISBN |
|
Additional Links |
UA library record; WoS full record; WoS citing articles |
Impact Factor |
6.7 |
Times cited |
|
Open Access |
OpenAccess |
Notes |
|
Approved |
Most recent IF: 6.7; 2023 IF: 7.367 |
Call Number |
UA @ admin @ c:irua:195249 |
Serial |
7340 |
Permanent link to this record |
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|
|
Author |
Milovanović, S.P.; Covaci, L.; Peeters, F.M. |
Title |
Strain fields in graphene induced by nanopillar mesh |
Type |
A1 Journal article |
Year |
2019 |
Publication |
Journal of applied physics |
Abbreviated Journal |
J Appl Phys |
Volume |
125 |
Issue |
8 |
Pages |
082534 |
Keywords |
A1 Journal article; Condensed Matter Theory (CMT) |
Abstract |
The mechanical and electronic properties of a graphene membrane placed on top of a triangular superlattice of nanopillars are investigated. We use molecular dynamics simulations to access the deformation fields and the tight-binding approaches to calculate the electronic properties. Ripples form in the graphene layer that span across the unit cell, connecting neighboring pillars, in agreement with recent experiments. We find that the resulting pseudo-magnetic field (PMF) varies strongly across the unit cell. We investigate the dependence of PMF on unit cell boundary conditions, height of the pillars, and the strength of the van der Waals interaction between graphene and the substrate. We find direct correspondence with typical experiments on pillars, showing intrinsic “slack” in the graphene membrane. PMF values are confirmed by the local density of states calculations performed at different positions of the unit cell showing pseudo-Landau levels with varying spacings. Our findings regarding the relaxed membrane configuration and the induced strains are transferable to other flexible 2D membranes. |
Address |
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Corporate Author |
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Thesis |
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Publisher |
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Place of Publication |
|
Editor |
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Language |
|
Wos |
000460033800038 |
Publication Date |
2019-01-16 |
Series Editor |
|
Series Title |
|
Abbreviated Series Title |
|
Series Volume |
|
Series Issue |
|
Edition |
|
ISSN |
0021-8979; 1089-7550 |
ISBN |
|
Additional Links |
UA library record; WoS full record; WoS citing articles |
Impact Factor |
2.068 |
Times cited |
9 |
Open Access |
|
Notes |
; S.P.M. is supported by the Flemish Science Foundation (FWO). ; |
Approved |
Most recent IF: 2.068 |
Call Number |
UA @ admin @ c:irua:158605 |
Serial |
5231 |
Permanent link to this record |
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|
|
Author |
Moldovan, D.; Masir, M.R.; Covaci, L.; Peeters, F.M. |
Title |
Resonant valley filtering of massive Dirac electrons |
Type |
A1 Journal article |
Year |
2012 |
Publication |
Physical review : B : condensed matter and materials physics |
Abbreviated Journal |
Phys Rev B |
Volume |
86 |
Issue |
11 |
Pages |
115431 |
Keywords |
A1 Journal article; Condensed Matter Theory (CMT) |
Abstract |
Electrons in graphene, in addition to their spin, have two pseudospin degrees of freedom: sublattice and valley pseudospin. Valleytronics uses the valley degree of freedom as a carrier of information similarly to the way spintronics uses electron spin. We show how a double-barrier structure consisting of electric and vector potentials can be used to filter massive Dirac electrons based on their valley index. We study the resonant transmission through a finite number of barriers and we obtain the energy spectrum of a superlattice consisting of electric and vector potentials. When a mass term is included, the energy bands and energy gaps at the K and K′ points are different and they can be tuned by changing the potential. |
Address |
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Corporate Author |
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Thesis |
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Publisher |
|
Place of Publication |
|
Editor |
|
Language |
|
Wos |
000309173300004 |
Publication Date |
2012-09-21 |
Series Editor |
|
Series Title |
|
Abbreviated Series Title |
|
Series Volume |
|
Series Issue |
|
Edition |
|
ISSN |
1098-0121;1550-235X; |
ISBN |
|
Additional Links |
UA library record; WoS full record; WoS citing articles |
Impact Factor |
3.836 |
Times cited |
55 |
Open Access |
|
Notes |
This work was supported by the European Science Foundation (ESF) under the EUROCORES Program Euro- GRAPHENE within the project CONGRAN, and the Flemish Science Foundation (FWO-Vl). |
Approved |
Most recent IF: 3.836; 2012 IF: 3.767 |
Call Number |
UA @ lucian @ c:irua:101835 |
Serial |
2896 |
Permanent link to this record |
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|
Author |
Berdiyorov, G.R.; Milošević, M.V.; Covaci, L.; Peeters, F.M. |
Title |
Rectification by an imprinted phase in a Josephson junction |
Type |
A1 Journal article |
Year |
2011 |
Publication |
Physical review letters |
Abbreviated Journal |
Phys Rev Lett |
Volume |
107 |
Issue |
17 |
Pages |
177008-177008,5 |
Keywords |
A1 Journal article; Condensed Matter Theory (CMT) |
Abstract |
A Josephson phase shift can be induced in a Josephson junction by a strategically nearby pinned Abrikosov vortex (AV). For an asymmetric distribution of an imprinted phase along the junction (controlled by the position of the AV) such a simple system is capable of rectification of ac current in a broad and tunable frequency range. The resulting rectified voltage is a consequence of the directed motion of a Josephson antivortex which forms a pair with the AV when at local equilibrium. The proposed realization of the ratchet potential by an imprinted phase is more efficient than the asymmetric geometry of the junction itself, is easily realizable experimentally, and provides rectification even in the absence of an applied magnetic field. |
Address |
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Corporate Author |
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Thesis |
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Publisher |
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Place of Publication |
New York, N.Y. |
Editor |
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Language |
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Wos |
000296985000008 |
Publication Date |
2011-10-21 |
Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
|
Series Issue |
|
Edition |
|
ISSN |
0031-9007;1079-7114; |
ISBN |
|
Additional Links |
UA library record; WoS full record; WoS citing articles |
Impact Factor |
8.462 |
Times cited |
28 |
Open Access |
|
Notes |
; This work was supported by the Flemish Science Foundation (FWO-Vlaanderen) and the Belgian Science Policy (IAP). G. R. B. and L. C. acknowledge individual support from FWO-Vlaanderen. ; |
Approved |
Most recent IF: 8.462; 2011 IF: 7.370 |
Call Number |
UA @ lucian @ c:irua:93715 |
Serial |
2847 |
Permanent link to this record |
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Author |
Garcia, J.H.; Covaci, L.; Rappoport, T.G. |
Title |
Real-space calculation of the conductivity tensor for disordered topological matter |
Type |
A1 Journal article |
Year |
2015 |
Publication |
Physical review letters |
Abbreviated Journal |
Phys Rev Lett |
Volume |
114 |
Issue |
114 |
Pages |
116602 |
Keywords |
A1 Journal article; Condensed Matter Theory (CMT) |
Abstract |
We describe an efficient numerical approach to calculate the longitudinal and transverse Kubo conductivities of large systems using Bastin's formulation. We expand the Green's functions in terms of Chebyshev polynomials and compute the conductivity tensor for any temperature and chemical potential in a single step. To illustrate the power and generality of the approach, we calculate the conductivity tensor for the quantum Hall effect in disordered graphene and analyze the effect of the disorder in a Chern insulator in Haldane's model on a honeycomb lattice. |
Address |
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Corporate Author |
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Thesis |
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Publisher |
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Place of Publication |
New York, N.Y. |
Editor |
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Language |
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Wos |
000351430600010 |
Publication Date |
2015-03-20 |
Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
|
Edition |
|
ISSN |
0031-9007;1079-7114; |
ISBN |
|
Additional Links |
UA library record; WoS full record; WoS citing articles |
Impact Factor |
8.462 |
Times cited |
69 |
Open Access |
|
Notes |
; We acknowledge A. R. Hernandez, A. Ferreira, and E. Mucciolo for discussions. T. G. R and J. H. G acknowledge the Brazilian agencies CNPq, FAPERJ, and INCT de Nanoestruturas de Carbono for financial support. L. C. acknowledges the Flemish Science Foundation (FWO-Vlaanderen) for financial support. ; |
Approved |
Most recent IF: 8.462; 2015 IF: 7.512 |
Call Number |
c:irua:125467 |
Serial |
2827 |
Permanent link to this record |
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Author |
Lin, S.-H.; Milošević, M.V.; Covaci, L.; Janko, B.; Peeters, F.M. |
Title |
Quantum rotor in nanostructured superconductors |
Type |
A1 Journal article |
Year |
2014 |
Publication |
Scientific reports |
Abbreviated Journal |
Sci Rep-Uk |
Volume |
4 |
Issue |
|
Pages |
4542-4546 |
Keywords |
A1 Journal article; Engineering sciences. Technology; Condensed Matter Theory (CMT) |
Abstract |
Despite its apparent simplicity, the idealized model of a particle constrained to move on a circle has intriguing dynamic properties and immediate experimental relevance. While a rotor is rather easy to set up classically, the quantum regime is harder to realize and investigate. Here we demonstrate that the quantum dynamics of quasiparticles in certain classes of nanostructured superconductors can be mapped onto a quantum rotor. Furthermore, we provide a straightforward experimental procedure to convert this nanoscale superconducting rotor into a regular or inverted quantum pendulum with tunable gravitational field, inertia, and drive. We detail how these novel states can be detected via scanning tunneling spectroscopy. The proposed experiments will provide insights into quantum dynamics and quantum chaos. |
Address |
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Corporate Author |
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Thesis |
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Publisher |
Nature Publishing Group |
Place of Publication |
London |
Editor |
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Language |
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Wos |
000333555300007 |
Publication Date |
2014-04-01 |
Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
|
ISSN |
2045-2322; |
ISBN |
|
Additional Links |
UA library record; WoS full record; WoS citing articles |
Impact Factor |
4.259 |
Times cited |
4 |
Open Access |
|
Notes |
; The work was supported by the Flemish Science Foundation (FWO-Vl), the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under contract W-31-109-Eng-38, and the US National Science Foundation via NSF-NIRT ECS-0609249. ; |
Approved |
Most recent IF: 4.259; 2014 IF: 5.578 |
Call Number |
UA @ lucian @ c:irua:116848 |
Serial |
2785 |
Permanent link to this record |
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Author |
Kim, W.; Covaci, L.; Dogan, F.; Marsiglio, F. |
Title |
Quantum mechanics of spin transfer in coupled electron-spin chains |
Type |
A1 Journal article |
Year |
2007 |
Publication |
Epl |
Abbreviated Journal |
Epl-Europhys Lett |
Volume |
79 |
Issue |
6 |
Pages |
67004 |
Keywords |
A1 Journal article |
Abstract |
The manner in which spin-polarized electrons interact with a magnetized thin film is currently described by a semi-classical approach. This in turn provides our present understanding of the spin transfer, or spin torque phenomenon. However, spin is an intrinsically quantum-mechanical quantity. Here, we make the first strides towards a fully quantum-mechanical description of spin transfer through spin currents interacting with a Heisenberg-coupled spin chain. Because of quantum entanglement, this requires a formalism based on the density matrix approach. Our description illustrates how individual spins in the chain time-evolve as a result of spin transfer. |
Address |
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Corporate Author |
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Thesis |
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Publisher |
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Place of Publication |
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Editor |
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Language |
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Wos |
000250409500023 |
Publication Date |
2007-08-24 |
Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
0295-5075 |
ISBN |
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Additional Links |
|
Impact Factor |
1.957 |
Times cited |
3 |
Open Access |
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Notes |
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Approved |
Most recent IF: 1.957; 2007 IF: 2.206 |
Call Number |
UA @ lucian @ |
Serial |
4430 |
Permanent link to this record |
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Author |
Zha, G.-Q.; Covaci, L.; Zhou, S.-P.; Peeters, F.M. |
Title |
Proximity-induced pseudogap in mesoscopic superconductor/normal-metal bilayers |
Type |
A1 Journal article |
Year |
2010 |
Publication |
Physical review : B : condensed matter and materials physics |
Abbreviated Journal |
Phys Rev B |
Volume |
82 |
Issue |
14 |
Pages |
140502-140502,4 |
Keywords |
A1 Journal article; Condensed Matter Theory (CMT) |
Abstract |
Recent scanning tunneling microscopy (STM) measurements of the proximity effect in Au/La2−xSrxCuO4 and La1.55Sr0.45CuO4/La2−xSrxCuO4 bilayers showed a proximity-induced pseudogap [O. Yuli, I. Asulin, Y. Kalcheim, G. Koren, and O. Millo, Phys. Rev. Lett. 103, 197003 (2009)]. We describe the proximity effect in mesoscopic superconductor/normal-metal bilayers by using the Bogoliubov-de Gennes equations for a tight-binding Hamiltonian with competing antiferromagnetic and d-wave superconductivity orders. The temperature-dependent local density of states is calculated as a function of the distance from the interface. Bound state due to both d-wave and spin-density wave gaps are formed in the normal metal for energies less than the respective gaps. If there is a mismatch between the Fermi velocities in the two layers we observe that these states will shift in energy when spin-density wave order is present, thus inducing a minigap at finite energy. We conclude that the STM measurement in the proximity structures is able to distinguish between the two scenarios proposed for the pseudogap (competing or precursor to superconductivity). |
Address |
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Corporate Author |
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Thesis |
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Publisher |
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Place of Publication |
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Editor |
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Language |
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Wos |
000282507200002 |
Publication Date |
2010-10-05 |
Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
1098-0121;1550-235X; |
ISBN |
|
Additional Links |
UA library record; WoS full record; WoS citing articles |
Impact Factor |
3.836 |
Times cited |
7 |
Open Access |
|
Notes |
; This work was supported by the Flemish Science Foundation (FWO-Vl), by Belgian Science Policy (IAP), by National Natural Science Foundation of China under Grants No. 10904089 and No. 60971053, by the Research Fund of Higher Education of China under Grant No. 20093108120005, by Shanghai Leading Academic Discipline project under Grant No. S30105, by Science and Technology Committee of Shanghai Municipal under Grant No. 09JC1406000, by Shanghai Municipal Education Committee under Grants No. shu-08053 and No. 10zz63, and by Innovation Funds of Shanghai University. ; |
Approved |
Most recent IF: 3.836; 2010 IF: 3.774 |
Call Number |
UA @ lucian @ c:irua:85028 |
Serial |
2735 |
Permanent link to this record |
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Author |
Covaci, L.; Marsiglio, F. |
Title |
Proximity effect and Josephson current in clean strong/weak/strong superconducting trilayers |
Type |
A1 Journal article |
Year |
2006 |
Publication |
Physical Review B |
Abbreviated Journal |
Phys Rev B |
Volume |
73 |
Issue |
1 |
Pages |
014503 |
Keywords |
A1 Journal article |
Abstract |
Recent measurements of the Josephson critical current through LSCO/LCO/LSCO thin films showed an unusually large proximity effect. Using the Bogoliubov-de Gennes equations for a tight-binding Hamiltonian we describe the proximity effect in weak links between a superconductor with critical temperature T-c and one with critical temperature T-c('), where T-c > T-c('). The weak link (N-') is therefore a superconductor above its own critical temperature and the superconducting regions are considered to have either s-wave or d-wave symmetry. We note that the proximity effect is enhanced due to the presence of superconducting correlations in the weak link. The dc Josephson current is calculated, and we obtain a nonzero value for temperatures greater than T-c(') for sizes of the weak links that can be almost an order of magnitude greater than the conventional coherence length. Considering pockets of superconductivity in the N-' layer, we show that this can lead to an even larger effect on the Josephson critical current by effectively shortening the weak link. |
Address |
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Corporate Author |
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Thesis |
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Publisher |
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Place of Publication |
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Editor |
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Language |
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Wos |
000235009000103 |
Publication Date |
2006-01-03 |
Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
1098-0121 |
ISBN |
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Additional Links |
|
Impact Factor |
3.836 |
Times cited |
31 |
Open Access |
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Notes |
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Approved |
Most recent IF: 3.836; 2006 IF: 3.107 |
Call Number |
UA @ lucian @ |
Serial |
4427 |
Permanent link to this record |