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Author Andelkovic, M.; Covaci, L.; Peeters, F.M.
Title DC conductivity of twisted bilayer graphene: Angle-dependent transport properties and effects of disorder Type A1 Journal article
Year 2018 Publication Physical review materials Abbreviated Journal (up)
Volume 2 Issue 3 Pages 034004
Keywords A1 Journal article; Condensed Matter Theory (CMT)
Abstract The in-plane dc conductivity of twisted bilayer graphene is calculated using an expansion of the real-space Kubo-Bastin conductivity in terms of Chebyshev polynomials. We investigate within a tight-binding approach the transport properties as a function of rotation angle, applied perpendicular electric field, and vacancy disorder. We find that for high-angle twists, the two layers are effectively decoupled, and the minimum conductivity at the Dirac point corresponds to double the value observed in monolayer graphene. This remains valid even in the presence of vacancies, hinting that chiral symmetry is still preserved. On the contrary, for low twist angles, the conductivity at the Dirac point depends on the twist angle and is not protected in the presence of disorder. Furthermore, for low angles and in the presence of an applied electric field, we find that the chiral boundary states emerging between AB and BA regions contribute to the dc conductivity, despite the appearance of localized states in the AA regions. The results agree qualitatively with recent transport experiments in low-angle twisted bilayer graphene.
Address
Corporate Author Thesis
Publisher American Physical Society Place of Publication College Park, Md Editor
Language Wos 000427822700002 Publication Date 2018-03-20
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 2475-9953 ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor Times cited 27 Open Access
Notes ; We acknowledge financial support from the graphene FLAG-ERA project TRANS2DTMD. ; Approved Most recent IF: NA
Call Number UA @ lucian @ c:irua:150838UA @ admin @ c:irua:150838 Serial 4964
Permanent link to this record
 
 
Author Wang, Z.; Wang, Y.B.; Yin, J.; Tovari, E.; Yang, Y.; Lin, L.; Holwill, M.; Birkbeck, J.; Perello, D.J.; Xu, S.; Zultak, J.; Gorbachev, R.V.; Kretinin, A.V.; Taniguchi, T.; Watanabe, K.; Morozov, S.V.; Andelkovic, M.; Milovanović, S.P.; Covaci, L.; Peeters, F.M.; Mishchenko, A.; Geim, A.K.; Novoselov, K.S.; Fal'ko, V.I.; Knothe, A.; Woods, C.R.
Title Composite super-moiré lattices in double-aligned graphene heterostructures = Composite super-moire lattices in double-aligned graphene heterostructures Type A1 Journal article
Year 2019 Publication Science Advances Abbreviated Journal (up)
Volume 5 Issue 12 Pages eaay8897
Keywords A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT); Condensed Matter Theory (CMT)
Abstract When two-dimensional (2D) atomic crystals are brought into close proximity to form a van der Waals heterostructure, neighbouring crystals may influence each other's properties. Of particular interest is when the two crystals closely match and a moire pattern forms, resulting in modified electronic and excitonic spectra, crystal reconstruction, and more. Thus, moire patterns are a viable tool for controlling the properties of 2D materials. However, the difference in periodicity of the two crystals limits the reconstruction and, thus, is a barrier to the low-energy regime. Here, we present a route to spectrum reconstruction at all energies. By using graphene which is aligned to two hexagonal boron nitride layers, one can make electrons scatter in the differential moire pattern which results in spectral changes at arbitrarily low energies. Further, we demonstrate that the strength of this potential relies crucially on the atomic reconstruction of graphene within the differential moire super cell.
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos 000505069600089 Publication Date 2019-12-21
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 2375-2548 ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor Times cited 49 Open Access
Notes Approved Most recent IF: NA
Call Number UA @ admin @ c:irua:165754 Serial 6289
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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 (up)
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.
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos 000692200800020 Publication Date 2021-08-31
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 1079-7114 ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor Times cited 4 Open Access OpenAccess
Notes Approved Most recent IF: NA
Call Number UA @ admin @ c:irua:181599 Serial 6896
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Author Conti, S.; Chaves, A.; Pandey, T.; Covaci, L.; Peeters, F.M.; Neilson, D.; Milošević, M.V.
Title Flattening conduction and valence bands for interlayer excitons in a moire MoS₂/WSe₂ heterobilayer Type A1 Journal article
Year 2023 Publication Nanoscale Abbreviated Journal (up)
Volume Issue Pages 1-11
Keywords A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT); Condensed Matter Theory (CMT)
Abstract We explore the flatness of conduction and valence bands of interlayer excitons in MoS2/WSe2 van der Waals heterobilayers, tuned by interlayer twist angle, pressure, and external electric field. We employ an efficient continuum model where the moire pattern from lattice mismatch and/or twisting is represented by an equivalent mesoscopic periodic potential. We demonstrate that the mismatch moire potential is too weak to produce significant flattening. Moreover, we draw attention to the fact that the quasi-particle effective masses around the Gamma-point and the band flattening are reduced with twisting. As an alternative approach, we show (i) that reducing the interlayer distance by uniform vertical pressure can significantly increase the effective mass of the moire hole, and (ii) that the moire depth and its band flattening effects are strongly enhanced by accessible electric gating fields perpendicular to the heterobilayer, with resulting electron and hole effective masses increased by more than an order of magnitude – leading to record-flat bands. These findings impose boundaries on the commonly generalized benefits of moire twistronics, while also revealing alternative feasible routes to achieve truly flat electron and hole bands to carry us to strongly correlated excitonic phenomena on demand.
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos 001047512300001 Publication Date 2023-07-25
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 Not_Open_Access: Available from 25.01.2024
Notes Approved Most recent IF: 6.7; 2023 IF: 7.367
Call Number UA @ admin @ c:irua:198290 Serial 8819
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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 (up)
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.
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos 000974675700006 Publication Date 2023-04-14
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 3.7 Times cited Open Access OpenAccess
Notes Approved Most recent IF: 3.7; 2023 IF: 3.836
Call Number UA @ admin @ c:irua:196709 Serial 8954
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Author Jorissen, B.; Covaci, L.; Partoens, B.
Title Comparative analysis of tight-binding models for transition metal dichalcogenides Type A1 Journal article
Year 2024 Publication SciPost physics core Abbreviated Journal (up)
Volume 7 Issue 1 Pages 004-30
Keywords A1 Journal article; Electron microscopy for materials research (EMAT); Condensed Matter Theory (CMT)
Abstract We provide a comprehensive analysis of the prominent tight-binding (TB) models for transition metal dichalcogenides (TMDs) available in the literature. We inspect the construction of these TB models, discuss their parameterization used and conduct a thorough comparison of their effectiveness in capturing important electronic properties. Based on these insights, we propose a novel TB model for TMDs designed for enhanced computational efficiency. Utilizing MoS2 as a representative case, we explain why specific models offer a more accurate description. Our primary aim is to assist researchers in choosing the most appropriate TB model for their calculations on TMDs.
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos Publication Date 2024-02-06
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN ISBN Additional Links UA library record
Impact Factor Times cited Open Access Not_Open_Access
Notes Approved no
Call Number UA @ admin @ c:irua:202983 Serial 9012
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Author Kourmoulakis, G.; Michail, A.; Paradisanos, I.; Marie, X.; Glazov, M.M.; Jorissen, B.; Covaci, L.; Stratakis, E.; Papagelis, K.; Parthenios, J.; Kioseoglou, G.
Title Biaxial strain tuning of exciton energy and polarization in monolayer WS2 Type A1 Journal Article
Year 2023 Publication Applied Physics Letters Abbreviated Journal (up)
Volume 123 Issue 22 Pages
Keywords A1 Journal Article; Condensed Matter Theory (CMT) ;
Abstract We perform micro-photoluminescence and Raman experiments to examine the impact of biaxial tensile strain on the optical properties of WS2 monolayers. A strong shift on the order of −130 meV per % of strain is observed in the neutral exciton emission at room temperature. Under near-resonant excitation, we measure a monotonic decrease in the circular polarization degree under the applied strain. We experimentally separate the effect of the strain-induced energy detuning and evaluate the pure effect coming from the biaxial strain. The analysis shows that the suppression of the circular polarization degree under the biaxial strain is related to an interplay of energy and polarization relaxation channels as well as to variations in the exciton oscillator strength affecting the long-range exchange interaction.
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos 001124156400003 Publication Date 2023-11-27
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0003-6951 ISBN Additional Links UA library record; WoS full record
Impact Factor 4 Times cited Open Access
Notes Hellenic Foundation for Research and Innovation, HFRI-FM17-3034 ; Approved Most recent IF: 4; 2023 IF: 3.411
Call Number CMT @ cmt @c:irua:202178 Serial 8991
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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 (up)
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
Corporate Author Thesis
Publisher Place of Publication Editor
Language 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
 
 
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 (up) 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.
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos 000760518100001 Publication Date 2022-04-01
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 2053-1583 ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor 5.5 Times cited 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
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Author Costamagna, S.; Schulz, A.; Covaci, L.; Peeters, F.
Title Partially unzipped carbon nanotubes as magnetic field sensors Type A1 Journal article
Year 2012 Publication Applied physics letters Abbreviated Journal (up) Appl Phys Lett
Volume 100 Issue 23 Pages 232104-232104,3
Keywords A1 Journal article; Condensed Matter Theory (CMT)
Abstract The conductance through graphene nanoribbons (GNR) connected to a partially unzipped carbon nanotube (CNT) is studied in the presence of an external magnetic field applied parallel to the long axis of the tube by means of non-equilibrium Green's function technique. We consider CNTs that are partially unzipped to form armchair-GNR/zigzag-CNT/armchair-GNR or zigzag-GNR/armchair-CNT/zigzag-GNR junctions. We find that the inclusion of a longitudinal magnetic field affects the electronic states only in the CNT region, leading to the suppression of the conductance at low energies. We demonstrate that both types of junctions can be used as magnetic field sensors. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4726039]
Address
Corporate Author Thesis
Publisher American Institute of Physics Place of Publication New York, N.Y. Editor
Language Wos 000305089900038 Publication Date 2012-06-07
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0003-6951; ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor 3.411 Times cited 10 Open Access
Notes ; L.C. acknowledges support from the Flemish Science Foundation (FWO-Vl) and S.C. from the Belgian Science Foundation (BELSPO). This work is supported by the ESF-EuroGRAPHENE Project CONGRAN. ; Approved Most recent IF: 3.411; 2012 IF: 3.794
Call Number UA @ lucian @ c:irua:99083 Serial 2556
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Author Homm, P.; Dillemans, L.; Menghini, M.; Van Bilzen, B.; Bakalov, P.; Su, C.Y.; Lieten, R.; Houssa, M.; Nasr Esfahani, D.; Covaci, L.; Peeters, F.M.; Seo, J.W.; Locquet, J.P.;
Title Collapse of the low temperature insulating state in Cr-doped V2O3 thin films Type A1 Journal article
Year 2015 Publication Applied physics letters Abbreviated Journal (up) Appl Phys Lett
Volume 107 Issue 107 Pages 111904
Keywords A1 Journal article; Condensed Matter Theory (CMT)
Abstract We have grown epitaxial Cr-doped V2O3 thin films with Cr concentrations between 0% and 20% on (0001)-Al2O3 by oxygen-assisted molecular beam epitaxy. For the highly doped samples (>3%), a regular and monotonous increase of the resistance with decreasing temperature is measured. Strikingly, in the low doping samples (between 1% and 3%), a collapse of the insulating state is observed with a reduction of the low temperature resistivity by up to 5 orders of magnitude. A vacuum annealing at high temperature of the films recovers the low temperature insulating state for doping levels below 3% and increases the room temperature resistivity towards the values of Cr-doped V2O3 single crystals. It is well-know that oxygen excess stabilizes a metallic state in V2O3 single crystals. Hence, we propose that Cr doping promotes oxygen excess in our films during deposition, leading to the collapse of the low temperature insulating state at low Cr concentrations. These results suggest that slightly Cr-doped V2O3 films can be interesting candidates for field effect devices. (C) 2015 AIP Publishing LLC.
Address
Corporate Author Thesis
Publisher American Institute of Physics Place of Publication New York, N.Y. Editor
Language Wos 000361639200020 Publication Date 2015-09-19
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0003-6951; 1077-3118 ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor 3.411 Times cited 14 Open Access
Notes ; The authors acknowledge financial support from the FWO Project No. G052010N10 as well as the EU-FP7 SITOGA Project. P.H. acknowledges support from Becas Chile-CONICYT. ; Approved Most recent IF: 3.411; 2015 IF: 3.302
Call Number UA @ lucian @ c:irua:128728 Serial 4149
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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 (up) 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.
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos 000598371500058 Publication Date 2020-09-17
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0008-6223 ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor 6.337 Times cited 11 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
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Author Zhang, L.-F.; Covaci, L.; Peeters, F.M.
Title Position-dependent effect of non-magnetic impurities on superconducting properties of nanowires Type A1 Journal article
Year 2015 Publication Europhysics letters Abbreviated Journal (up) Epl-Europhys Lett
Volume 109 Issue 109 Pages 17010
Keywords A1 Journal article; Condensed Matter Theory (CMT)
Abstract Anderson's theorem states that non-magnetic impurities do not change the bulk properties of conventional superconductors. However, as the dimensionality is reduced, the effect of impurities becomes more significant. Here we investigate superconducting nanowires with diameter comparable to the Fermi wavelength $\lambda_F$ (which is less than the superconducting coherence length) by using a microscopic description based on the Bogoliubov-de Gennes method. We find that: 1) impurities strongly affect the superconducting properties, 2) the effect is impurity position dependent, and 3) it exhibits opposite behavior for resonant and off-resonant wire widths. We show that this is due to the interplay between the shape resonances of the order parameter and the subband energy spectrum induced by the lateral quantum confinement. These effects can be used to manipulate the Josephson current, filter electrons by subband and investigate the symmetries of the superconducting subband gaps.
Address
Corporate Author Thesis
Publisher Place of Publication Paris Editor
Language Wos 000348592100029 Publication Date 2015-01-21
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0295-5075 ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor 1.957 Times cited 7 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: 1.957; 2015 IF: 2.095
Call Number UA @ lucian @ c:irua:128424 Serial 4227
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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 (up) 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
Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos 000250409500023 Publication Date 2007-08-24
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0295-5075 ISBN Additional Links
Impact Factor 1.957 Times cited 3 Open Access
Notes Approved Most recent IF: 1.957; 2007 IF: 2.206
Call Number UA @ lucian @ Serial 4430
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Author Covaci, L.; Berciu, M.
Title Holstein polaron: The effect of coupling to multiple-phonon modes Type A1 Journal article
Year 2007 Publication Epl Abbreviated Journal (up) Epl-Europhys Lett
Volume 80 Issue 6 Pages 67001
Keywords A1 Journal article
Abstract We investigate the effects of coupling to multiple-phonon modes on the properties of a Holstein polaron. To this end, we generalize the Momentum Average approximations MA((0)) and MA((1)) to deal with multiple-phonon modes. As for a single-phonon mode, these approximations are found to be numerically very efficient. They become exact for very weak or very strong couplings, and are highly accurate in the intermediate regimes, e.g. the spectral weights obey exactly the first six, respectively eight, sum rules. Our results show that the effect on ground-state properties is cumulative in nature. As a result, if the effective coupling to one mode is much larger than to all the others, this mode effectively determines the ground-state properties. However, even very weak coupling to a second phonon mode has important non-perturbational effects on the higher-energy spectrum, in particular on the dispersion and the phonon statistics of the polaron band. This has important consequences on the analysis and interpretation of data for real materials.
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos 000251648300016 Publication Date 2007-11-30
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0295-5075 ISBN Additional Links
Impact Factor 1.957 Times cited 9 Open Access
Notes Approved Most recent IF: 1.957; 2007 IF: 2.206
Call Number UA @ lucian @ Serial 4431
Permanent link to this record
 
 
Author Berdiyorov, G.R.; de Romaguera, A.R.C.; Milošević, M.V.; Doria, M.M.; Covaci, L.; Peeters, F.M.
Title Dynamic and static phases of vortices under an applied drive in a superconducting stripe with an array of weak links Type A1 Journal article
Year 2012 Publication European physical journal : B : condensed matter and complex systems Abbreviated Journal (up) Eur Phys J B
Volume 85 Issue 4 Pages 130-130,8
Keywords A1 Journal article; Condensed Matter Theory (CMT)
Abstract Static and dynamic properties of superconducting vortices in a superconducting stripe with a periodic array of weakly-superconducting (or normal metal) regions are studied in the presence of external magnetic and electric fields. The time-dependent Ginzburg-Landau theory is used to describe the electronic transport, where the anisotropy is included through the spatially-dependent critical temperature T-c. Superconducting vortices penetrating into the weak-superconducting region with smaller T-c are more mobile than the ones in the strong superconducting regions. We observe periodic entrance and exit of vortices which reside in the weak link for some short interval. The mobility of the weakly-pinned vortices can be reduced by increasing the uniform applied magnetic field leading to distinct features in the voltage vs. magnetic field response of the system.
Address
Corporate Author Thesis
Publisher Place of Publication Berlin Editor
Language Wos 000303545400013 Publication Date 2012-04-20
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 1434-6028;1434-6036; ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor 1.461 Times cited 32 Open Access
Notes ; This work was supported by the Flemish Science Foundation (FWO-Vl), the Belgian Science Policy (IAP), the bilateral programme between Flanders and Brazil. G.R.B. and L.C. acknowledge individual support from FWO-Vl. A.R.de C.R. acknowledges CNPq and FACEPE for financial support. ; Approved Most recent IF: 1.461; 2012 IF: 1.282
Call Number UA @ lucian @ c:irua:98267 Serial 761
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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 (up) 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
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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 (up) 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
Corporate Author Thesis
Publisher Place of Publication Editor
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 5 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
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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 (up) 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.
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos 000576393200002 Publication Date 2020-09-28
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 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
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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 (up) 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 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
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Author Andelkovic, M.; Milovanović, S.P.; Covaci, L.; Peeters, F.M.
Title Double moiré with a twist : supermoiré in encapsulated graphene Type A1 Journal article
Year 2020 Publication Nano Letters Abbreviated Journal (up) Nano Lett
Volume 20 Issue 2 Pages 979
Keywords A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT); Condensed Matter Theory (CMT)
Abstract A periodic spatial modulation, as created by a moire pattern, has been extensively studied with the view to engineer and tune the properties of graphene. Graphene encapsulated by hexagonal boron nitride (hBN) when slightly misaligned with the top and bottom hBN layers experiences two interfering moire patterns, resulting in a so-called supermoire (SM). This leads to a lattice and electronic spectrum reconstruction. A geometrical construction of the nonrelaxed SM patterns allows us to indicate qualitatively the induced changes in the electronic properties and to locate the SM features in the density of states and in the conductivity. To emphasize the effect of lattice relaxation, we report band gaps at all Dirac-like points in the hole doped part of the reconstructed spectrum, which are expected to be enhanced when including interaction effects. Our result is able to distinguish effects due to lattice relaxation and due to the interfering SM and provides a clear picture on the origin of recently experimentally observed effects in such trilayer heterostuctures.
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos 000514255400021 Publication Date 2020-01-21
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 1530-6984 ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor 10.8 Times cited 33 Open Access OpenAccess
Notes ; This work was funded by FLAGERA project TRANS2DTMD and the Flemish Science Foundation (FWO-Vl) through a postdoc fellowship for S.P.M. The authors acknowledge useful discussions with W. Zihao and K. Novoselov. ; Approved Most recent IF: 10.8; 2020 IF: 12.712
Call Number UA @ admin @ c:irua:168685 Serial 6490
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Author Villarreal, R.; Lin, P.-C.; Faraji, F.; Hassani, N.; Bana, H.; Zarkua, Z.; Nair, M.N.; Tsai, H.-C.; Auge, M.; Junge, F.; Hofsaess, H.C.; De Gendt, S.; De Feyter, S.; Brems, S.; Ahlgren, E.H.; Neyts, E.C.; Covaci, L.; Peeters, F.M.; Neek-Amal, M.; Pereira, L.M.C.
Title Breakdown of universal scaling for nanometer-sized bubbles in graphene Type A1 Journal article
Year 2021 Publication Nano Letters Abbreviated Journal (up) Nano Lett
Volume 21 Issue 19 Pages 8103-8110
Keywords A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT); Condensed Matter Theory (CMT); Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Abstract We report the formation of nanobubbles on graphene with a radius of the order of 1 nm, using ultralow energy implantation of noble gas ions (He, Ne, Ar) into graphene grown on a Pt(111) surface. We show that the universal scaling of the aspect ratio, which has previously been established for larger bubbles, breaks down when the bubble radius approaches 1 nm, resulting in much larger aspect ratios. Moreover, we observe that the bubble stability and aspect ratio depend on the substrate onto which the graphene is grown (bubbles are stable for Pt but not for Cu) and trapped element. We interpret these dependencies in terms of the atomic compressibility of the noble gas as well as of the adhesion energies between graphene, the substrate, and trapped atoms.
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos 000709549100026 Publication Date 2021-09-14
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 1530-6984 ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor 12.712 Times cited 12 Open Access OpenAccess
Notes Approved Most recent IF: 12.712
Call Number UA @ admin @ c:irua:184137 Serial 6857
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Author Mao, J.; Milovanović, S.P.; Andelkovic, M.; Lai, X.; Cao, Y.; Watanabe, K.; Taniguchi, T.; Covaci, L.; Peeters, F.M.; Geim, A.K.; Jiang, Y.; Andrei, E.Y.
Title Evidence of flat bands and correlated states in buckled graphene superlattices Type A1 Journal article
Year 2020 Publication Nature Abbreviated Journal (up) Nature
Volume 584 Issue 7820 Pages 215-220
Keywords A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT); Condensed Matter Theory (CMT)
Abstract Two-dimensional atomic crystals can radically change their properties in response to external influences, such as substrate orientation or strain, forming materials with novel electronic structure(1-5). An example is the creation of weakly dispersive, 'flat' bands in bilayer graphene for certain 'magic' angles of twist between the orientations of the two layers(6). The quenched kinetic energy in these flat bands promotes electron-electron interactions and facilitates the emergence of strongly correlated phases, such as superconductivity and correlated insulators. However, the very accurate fine-tuning required to obtain the magic angle in twisted-bilayer graphene poses challenges to fabrication and scalability. Here we present an alternative route to creating flat bands that does not involve fine-tuning. Using scanning tunnelling microscopy and spectroscopy, together with numerical simulations, we demonstrate that graphene monolayers placed on an atomically flat substrate can be forced to undergo a buckling transition(7-9), resulting in a periodically modulated pseudo-magnetic field(10-14), which in turn creates a 'post-graphene' material with flat electronic bands. When we introduce the Fermi level into these flat bands using electrostatic doping, we observe a pseudogap-like depletion in the density of states, which signals the emergence of a correlated state(15-17). This buckling of two-dimensional crystals offers a strategy for creating other superlattice systems and, in particular, for exploring interaction phenomena characteristic of flat bands. Buckled monolayer graphene superlattices are found to provide an alternative to twisted bilayer graphene for the study of flat bands and correlated states in a carbon-based material.
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos 000559831500012 Publication Date 2020-08-12
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0028-0836 ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor 64.8 Times cited 75 Open Access Not_Open_Access
Notes ; ; Approved Most recent IF: 64.8; 2020 IF: 40.137
Call Number UA @ admin @ c:irua:171150 Serial 6513
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Author García, J.H.; Uchoa, B.; Covaci, L.; Rappoport, T.G.
Title Adatoms and Anderson localization in graphene Type A1 Journal article
Year 2014 Publication Physical review : B : condensed matter and materials physics Abbreviated Journal (up) Phys Rev B
Volume 90 Issue 8 Pages 085425
Keywords A1 Journal article; Condensed Matter Theory (CMT)
Abstract We address the nature of the disordered state that results from the adsorption of adatoms in graphene. For adatoms that sit at the center of the honeycomb plaquette, as in the case of most transition metals, we show that the ones that form a zero-energy resonant state lead to Anderson localization in the vicinity of the Dirac point. Among those, we show that there is a symmetry class of adatoms where Anderson localization is suppressed, leading to an exotic metallic state with large and rare charge droplets, that localizes only at the Dirac point. We identify the experimental conditions for the observation of the Anderson transition for adatoms in graphene.
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos 000341238600004 Publication Date 2014-08-22
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 12 Open Access
Notes ; We acknowledge F. Guinea, K. Mullen, A. H. Castro Neto, and E. Mucciolo for discussions. B. U. acknowledges the University of Oklahoma for financial support and NSF Grant No. DMR-1352604 for partial support. T.G.R. and J.H.G acknowledge Brazilian agencies CNPq, FAPERJ, and “INCT de nanoestruturas de carbono” for financial support. ; Approved Most recent IF: 3.836; 2014 IF: 3.736
Call Number UA @ lucian @ c:irua:119258 Serial 57
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Author Nasr Esfahani, D.; Covaci, L.; Peeters, F.M.
Title Electric-field-induced shift of the Mott metal-insulator transition in thin films Type A1 Journal article
Year 2012 Publication Physical review : B : condensed matter and materials physics Abbreviated Journal (up) Phys Rev B
Volume 85 Issue 8 Pages 085110-085110,8
Keywords A1 Journal article; Condensed Matter Theory (CMT)
Abstract The ground-state properties of a paramagnetic Mott insulator at half-filling are investigated in the presence of an external electric field using the inhomogeneous Gutzwiller approximation for a single-band Hubbard model in a slab geometry. We find that the metal-insulator transition is shifted toward higher Hubbard repulsions by applying an electric field perpendicular to the slab. The main reason is the accumulation of charges near the surface. The spatial distribution of site-dependent quasiparticle weight shows that it is maximal in a few layers beneath the surface, while the central sites where the field is screened have a very low quasiparticle weight. Our results show that above a critical-field value, states near the surface will be metallic, while the bulk quasiparticle weight is extremely suppressed but never vanishing, even for large Hubbard repulsions above the bulk zero-field critical value. Below the critical-field value, our results hint toward an insulating state in which the electric field is totally screened and the slab is again at half-filling.
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos 000300240100002 Publication Date 2012-02-14
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 3 Open Access
Notes ; This work was supported by the Flemish Science Foundation (FWO-Vlaanderen) and the Belgian Science Policy (IAP). ; Approved Most recent IF: 3.836; 2012 IF: 3.767
Call Number UA @ lucian @ c:irua:97208 Serial 884
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Author Neek-Amal, M.; Covaci, L.; Shakouri, K.; Peeters, F.M.
Title Electronic structure of a hexagonal graphene flake subjected to triaxial stress Type A1 Journal article
Year 2013 Publication Physical review : B : condensed matter and materials physics Abbreviated Journal (up) Phys Rev B
Volume 88 Issue 11 Pages 115428
Keywords A1 Journal article; Condensed Matter Theory (CMT)
Abstract The electronic properties of a triaxially strained hexagonal graphene flake with either armchair or zigzag edges are investigated using molecular dynamics simulations and tight-binding calculations. We found that (i) the pseudomagnetic field in strained graphene flakes is not uniform neither in the center nor at the edge of zigzag terminated flakes, (ii) the pseudomagnetic field is almost zero in the center of armchair terminated flakes but increases dramatically near the edges, (iii) the pseudomagnetic field increases linearly with strain, for strains lower than 15% but increases nonlinearly beyond it, (iv) the local density of states in the center of the zigzag hexagon exhibits pseudo-Landau levels with broken sublattice symmetry in the zeroth pseudo-Landau level, and in addition there is a shift in the Dirac cone due to strain induced scalar potentials, and (v) there is size effect in pseudomagnetic field. This study provides a realistic model of the electronic properties of inhomogeneously strained graphene where the relaxation of the atomic positions is correctly included together with strain induced modifications of the hopping terms up to next-nearest neighbors.
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos 000324690400008 Publication Date 2013-09-24
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 46 Open Access
Notes ; This work was supported by the EU-Marie Curie IIF postdoctoral Fellowship/ 299855 (for M.N.-A.), the ESF EuroGRAPHENE project CONGRAN, 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:111168 Serial 1011
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Author Esfahani, D.N.; Covaci, L.; Peeters, F.M.
Title Field effect on surface states in a doped Mott-insulator thin film Type A1 Journal article
Year 2013 Publication Physical review : B : condensed matter and materials physics Abbreviated Journal (up) Phys Rev B
Volume 87 Issue 3 Pages 035131-35136
Keywords A1 Journal article; Condensed Matter Theory (CMT)
Abstract Surface effects of a doped thin film made of a strongly correlated material are investigated both in the absence and presence of a perpendicular electric field. We use an inhomogeneous Gutzwiller approximation for a single-band Hubbard model in order to describe correlation effects. For low doping, the bulk value of the quasiparticle weight is recovered exponentially deep into the slab, but with increasing doping, additional Friedel oscillations appear near the surface. We show that the inverse correlation length has a power-law dependence on the doping level. In the presence of an electrical field, considerable changes in the quasiparticle weight can be realized throughout the system. We observe a large difference (as large as five orders of magnitude) in the quasiparticle weight near the opposite sides of the slab. This effect can be significant in switching devices that use the surface states for transport. DOI: 10.1103/PhysRevB.87.035131
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos 000313941000001 Publication Date 2013-01-29
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-VI). ; Approved Most recent IF: 3.836; 2013 IF: 3.664
Call Number UA @ lucian @ c:irua:110086 Serial 1190
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Author Li, Z.; Covaci, L.; Marsiglio, F.
Title Impact of Dresselhaus versus Rashba spin-orbit coupling on the Holstein polaron Type A1 Journal article
Year 2012 Publication Physical review : B : condensed matter and materials physics Abbreviated Journal (up) Phys Rev B
Volume 85 Issue 20 Pages 205112-205112,5
Keywords A1 Journal article; Condensed Matter Theory (CMT)
Abstract We utilize an exact variational numerical procedure to calculate the ground-state properties of a polaron in the presence of Rashba and linear Dresselhaus spin-orbit coupling. We find that when the linear Dresselhaus spin-orbit coupling approaches the Rashba spin-orbit coupling, the Van Hove singularity in the density of states will be shifted away from the bottom of the band and finally disappear when the two spin-orbit couplings are tuned to be equal. The effective mass will be suppressed; the trend will become more significant for low phonon frequency. The presence of two dominant spin-orbit couplings will make it possible to tune the effective mass with more varied observables.
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos 000303794900003 Publication Date 2012-05-09
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 18 Open Access
Notes ; This work was supported in part by the Natural Sciences and Engineering Research Council of Canada (NSERC), by ICORE (Alberta), by the Flemish Science Foundation (FWO-Vl), and by the Canadian Institute for Advanced Research (CIfAR). ; Approved Most recent IF: 3.836; 2012 IF: 3.767
Call Number UA @ lucian @ c:irua:99121 Serial 1558
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Author Li, Z.; Covaci, L.; Berciu, M.; Baillie, D.; Marsiglio, F.
Title Impact of spin-orbit coupling on the Holstein polaron Type A1 Journal article
Year 2011 Publication Physical review : B : condensed matter and materials physics Abbreviated Journal (up) Phys Rev B
Volume 83 Issue 19 Pages 195104-195104,9
Keywords A1 Journal article; Condensed Matter Theory (CMT)
Abstract We utilize an exact variational numerical procedure to calculate the ground state properties of a polaron in the presence of a Rashba-like spin-orbit interaction. Our results corroborate previous work performed with the momentum average approximation and with weak-coupling perturbation theory. We find that spin-orbit coupling increases the effective mass in the regime with weak electron-phonon coupling, and decreases the effective mass in the regimes of intermediate and strong electron-phonon coupling. Analytical strong-coupling perturbation theory results confirm our numerical results in the small-polaron regime. A large amount of spin-orbit coupling can lead to a significant lowering of the polaron effective mass.
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos 000290162500001 Publication Date 2011-05-03
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 9 Open Access
Notes ; This work was supported in part by the Natural Sciences and Engineering Research Council of Canada (NSERC), by ICORE (Alberta), by Alberta Ingenuity, by the Flemish Science Foundation (FWO-Vl), and by the Canadian Institute for Advanced Research (CIfAR). ; Approved Most recent IF: 3.836; 2011 IF: 3.691
Call Number UA @ lucian @ c:irua:89718 Serial 1561
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Author Zha, G.-Q.; Covaci, L.; Peeters, F.M.; Zhou, S.-P.
Title Majorana fermion states and fractional flux periodicity in mesoscopic d-wave superconducting loops with spin-orbit interaction Type A1 Journal article
Year 2014 Publication Physical review : B : condensed matter and materials physics Abbreviated Journal (up) Phys Rev B
Volume 90 Issue 1 Pages 014522
Keywords A1 Journal article; Condensed Matter Theory (CMT)
Abstract We numerically investigate the spin-orbit (SO) coupling effect on the magnetic flux evolution of energy and supercurrent in mesoscopic d-wave superconducting loops by solving the spin-generalized Bogoliubov-de Gennes equations self-consistently. It is found that the energy spectrum splits when the SO interaction is involved and the Majorana zero mode can be realized in the [100] edges of square systems for an appropriate SO coupling strength. Superconducting phase transitions appear when the energy gap closes, accompanied by energy jumps between different energy parabolas in the ground state, which provides a possible mechanism to support fractional flux periodicity of supercurrent. Moreover, in the case of rectangular loops with SO coupling, the jumps of the ground-state energy gradually disappear by increasing the ratio of length to height of the sample, and a paramagnetic response with opposite direction of the screening current around zero flux value can occur in such systems.
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos 000341233800010 Publication Date 2014-07-31
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 7 Open Access
Notes ; This work was supported by National Natural Science Foundation of China under Grants No. 61371020 and No. 61271163, by Visiting Scholar Program of Shanghai Municipal Education Commission, by Innovation Program of Shanghai Municipal Education Commission under Grant No. 13YZ006, and by the Flemish Science Foundation (FWO-Vl). ; Approved Most recent IF: 3.836; 2014 IF: 3.736
Call Number UA @ lucian @ c:irua:119266 Serial 1938
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