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“Temporary cooling of quasiparticles and delay in voltage response of superconducting bridges after abruptly switching on the supercritical current”. Vodolazov DY, Peeters FM, Physical review : B : condensed matter and materials physics 90, 094504 (2014). http://doi.org/10.1103/PhysRevB.90.094504
Abstract: We revisit the problem of the dynamic response of a superconducting bridge after abruptly switching on the supercritical current. In contrast to previous theoretical works we take into account spatial gradients and use both the local temperature approach and the kinetic equation for the distribution function of quasiparticles. We find that the temperature dependence of the finite delay time t(d) in the voltage response is model dependent and relatively large t(d) is connected with temporary cooling of quasiparticles during decay of superconducting order parameter vertical bar Delta vertical bar in time. It turns out that the presence of even small inhomogeneities in the bridge or finite length of the homogenous bridge favors a local suppression of vertical bar Delta vertical bar during the dynamic response. It results in a decrease of the delay time, in comparison with the spatially uniform model, due to the diffusion of nonequilibrium quasiparticles from the region with locally suppressed vertical bar Delta vertical bar. In the case when the current density is maximal near the edge of a not very wide bridge the delay time is mainly connected with the time needed for the nucleation (entrance) of the first vortex and t(d) could be tuned by a weak external magnetic field. We also find that a short alternating current pulse (sinusoidlike) with zero time average may result in a nonzero time- averaged voltage response where its sign depends on the phase of the ac current.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 2
DOI: 10.1103/PhysRevB.90.094504
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“Angle-resolved synchrotron photoemission and density functional theory on the iridium modified Si(111) surface”. Oncel N, Çakir D, Dil JH, Slomski B, Landolt G, Journal of physics : condensed matter 26, 285501 (2014). http://doi.org/10.1088/0953-8984/26/28/285501
Abstract: The physical and electronic properties of the Ir modified Si(1 1 1) surface have been investigated with the help of angle resolved photoemission spectroscopy and density functional theory. The surface consists of Ir-ring clusters that form a root 7 x root 7 -R19.1 degrees reconstruction. A comparison between the measured and calculated band structure of the system reveals that the dispersions of the projected bulk states and the states originating from '1x1' domains are heavily modified due to Umklapp scattering from the surface Brillouin zone. Density of states calculations show that Ir-ring clusters contribute to the states in the vicinity of the Fermi level.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.649
Times cited: 4
DOI: 10.1088/0953-8984/26/28/285501
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“Transition metal dichalcogenides as strategy for high temperature electron-hole superfluidity”. Conti S, Neilson D, Peeters FM, Perali A, Condensed Matter 5, 22 (2020). http://doi.org/10.3390/CONDMAT5010022
Abstract: Condensation of spatially indirect excitons, with the electrons and holes confined in two separate layers, has recently been observed in two different double layer heterostructures. High transition temperatures were reported in a double Transition Metal Dichalcogenide (TMD) monolayer system. We briefly review electron-hole double layer systems that have been proposed as candidates for this interesting phenomenon. We investigate the double TMD system WSe2/hBN/MoSe2, using a mean-field approach that includes multiband effects due to the spin-orbit coupling and self-consistent screening of the electron-hole Coulomb interaction. We demonstrate that the transition temperature observed in the double TMD monolayers, which is remarkably high relative to the other systems, is the result of (i) the large electron and hole effective masses in TMDs, (ii) the large TMD band gaps, and (iii) the presence of multiple superfluid condensates in the TMD system. The net effect is that the superfluidity is strong across a wide range of densities, which leads to high transition temperatures that extend as high as TBKT=150 K.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Times cited: 13
DOI: 10.3390/CONDMAT5010022
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“Oscillating spin-orbit interaction in two-dimensional superlattices : sharp transmission resonances and time-dependent spin-polarized currents”. Szaszko-Bogar V, Peeters FM, Foeldi P, Physical review : B : condensed matter and materials physics 91, 235311 (2015). http://doi.org/10.1103/PhysRevB.91.235311
Abstract: We consider ballistic transport through a lateral, two-dimensional superlattice with experimentally realizable, sinusoidally oscillating, Rashba-type spin-orbit interaction (SOI). The periodic structure of the rectangular lattice produces a spin-dependent miniband structure for static SOI. Using Floquet theory, transmission peaks are shown to appear in themini-bandgaps as a consequence of the additional, time-dependent SOI. A detailed analysis shows that this effect is due to the generation of harmonics of the driving frequency, via which, e.g., resonances that cannot be excited in the case of static SOI become available. Additionally, the transmitted current shows space-and time-dependent partial spin polarization, in other words, polarization waves propagate through the superlattice.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 10
DOI: 10.1103/PhysRevB.91.235311
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“Effective spin-orbit interaction Hamiltonian for quasi-one-dimensional quantum rings”. Shakouri K, Szafran B, Esmaeilzadeh M, Peeters FM, Physical review : B : condensed matter and materials physics 85, 165314 (2012). http://doi.org/10.1103/PhysRevB.85.165314
Abstract: The effective Hamiltonian for an electron in a quasi-one-dimensional quantum ring in the presence of spin-orbit interactions is derived. We demonstrate that, when both coupling types are simultaneously present, the effective Hamiltonian derived by the lowest-radial-state approximation produces energy spectra and charge densities which deviate strongly from the exact ones. For equal Rashba and Dresselhaus coupling constants the lowest-radial-state approximation opens artifactal avoided crossings in the energy spectra and deforms the circular symmetry of the confined charge densities. In this case, there does not exist a ring thin enough to justify the restriction to the lowest radially quantized energy state. We derive the effective Hamiltonian accounting for both the lowest and the first excited radial states, and show that the inclusion of the latter restores the correct features of the exact solution. Relation of this result to the states of a quantum wire is also discussed.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 32
DOI: 10.1103/PhysRevB.85.165314
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“Electric-field-driven Mott metal-insulator transition in correlated thin films : an inhomogeneous dynamical mean-field theory approach”. Bakalov P, Esfahani DN, Covaci L, Peeters FM, Tempere J, Locquet J-P, Physical review : B : condensed matter and materials physics 93, 165112 (2016). http://doi.org/10.1103/PhysRevB.93.165112
Abstract: Simulations are carried out based on the dynamical mean-field theory (DMFT) in order to investigate the properties of correlated thin films for various values of the chemical potential, temperature, interaction strength, and applied transverse electric field. Application of a sufficiently strong field to a thin film at half filling leads to the appearance of conducting regions near the surfaces of the film, whereas in doped slabs the application of a field leads to a conductivity enhancement on one side of the film and a gradual transition to the insulating state on the opposite side. In addition to the inhomogeneous DMFT, a local density approximation (LDA) is considered in which the particle density n, quasiparticle residue Z, and spectral weight at the Fermi level A(ω=0) of each layer are approximated by a homogeneous bulk environment. A systematic comparison between the two approaches reveals that the less expensive LDA results are in good agreement with the DMFT approach, except close to the metal-to-insulator transition points and in the layers immediately at the film surfaces. LDA values for n are overall more reliable than those for Z and A(ω=0). The hysteretic behavior (memory effect) characteristic of the bulk doping driven Mott transition persists in the slab.
Keywords: A1 Journal article; Theory of quantum systems and complex systems; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 5
DOI: 10.1103/PhysRevB.93.165112
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“Tubular fullerenes inside carbon nanotubes : optimal molecular orientation versus tube radius”. Verberck B, Tarakina NV, European physical journal : B : condensed matter and complex systems 80, 355 (2011). http://doi.org/10.1140/epjb/e2011-10952-1
Abstract: We present an investigation of the orientations and positions of tubular fullerene molecules (C90, ..., C200) encapsulated in single-walled carbon nanotubes (SWCNT), a series of so-called fullerene nanopeapods. We find that increasing the tube radius leads to the following succession of energetically stable regimes: (1) lying molecules positioned on the tube's long axis; (2) tilted molecules on the tube's long axis; and (3) lying molecules shifted away from the tube's long axis. As opposed to C70 and C80 molecules encapsulated in a SWCNT, standing orientations do not develop. Our results are relevant for the possible application of molecular-orientation-dependent electronic properties of fullerene nanopeapods, and also for the interpretation of future experiments on double-walled carbon nanotube formation by annealing fullerene peapod systems.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Condensed Matter Theory (CMT)
Impact Factor: 1.461
Times cited: 10
DOI: 10.1140/epjb/e2011-10952-1
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“Vortex detection and quantum transport in mesoscopic graphene Josephson-junction arrays”. Richardson CL, Edkins SD, Berdiyorov GR, Chua CJ, Griffiths JP, Jones GAC, Buitelaar MR, Narayan V, Sfigakis F, Smith CG, Covaci L, Connolly MR;, Physical review : B : condensed matter and materials physics 91, 245418 (2015). http://doi.org/10.1103/PhysRevB.91.245418
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.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 2
DOI: 10.1103/PhysRevB.91.245418
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“Magnetic field induced vortices in graphene quantum dots”. Lavor IR, da Costa DR, Chaves A, Farias GA, Macedo R, Peeters FM, Journal Of Physics-Condensed Matter 32, 155501 (2020). http://doi.org/10.1088/1361-648X/AB6463
Abstract: The energy spectrum and local current patterns in graphene quantum dots (QD) are investigated for different geometries in the presence of an external perpendicular magnetic field. Our results demonstrate that, for specific geometries and edge configurations, the QD exhibits vortex and anti-vortex patterns in the local current density, in close analogy to the vortex patterns observed in the probability density current of semiconductor QD, as well as in the order parameter of mesoscopic superconductors.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.7
Times cited: 5
DOI: 10.1088/1361-648X/AB6463
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“Braess paradox at the mesoscopic scale”. de Sousa AA, Chaves A, Farias GA, Peeters FM, Physical review : B : condensed matter and materials physics 88, 245417 (2013). http://doi.org/10.1103/PhysRevB.88.245417
Abstract: We theoretically demonstrate that the transport inefficiency recently found experimentally for branched-out mesoscopic networks can also be observed in a quantum ring of finite width with an attached central horizontal branch. This is done by investigating the time evolution of an electron wave packet in such a system. Our numerical results show that the conductivity of the ring does not necessary improve if one adds an extra channel. This ensures that there exists a quantum analog of the Braess paradox, originating from quantum scattering and interference.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 17
DOI: 10.1103/PhysRevB.88.245417
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“Valley filtering using electrostatic potentials in bilayer graphene”. da Costa DR, Chaves A, Sena SHR, Farias GA, Peeters FM, Physical review : B : condensed matter and materials physics 92, 045417 (2015). http://doi.org/10.1103/PhysRevB.92.045417
Abstract: Propagation of an electron wave packet through a quantum point contact (QPC) defined by electrostatic gates in bilayer graphene is investigated. The gates provide a bias between the layers, in order to produce an energy gap. If the gates on both sides of the contact produce the same bias, steps in the electron transmission probability are observed, as in the usual QPC. However, if the bias is inverted on one of the sides of the QPC, only electrons belonging to one of the Dirac valleys are allowed to pass, which provides a very efficient valley filtering.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 47
DOI: 10.1103/PhysRevB.92.045417
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“Energy levels of bilayer graphene quantum dots”. da Costa DR, Zarenia M, Chaves A, Farias GA, Peeters FM, Physical review : B : condensed matter and materials physics 92, 115437 (2015). http://doi.org/10.1103/PhysRevB.92.115437
Abstract: Within a tight binding approach we investigate the energy levels of hexagonal and triangular bilayer graphene (BLG) quantum dots (QDs) with zigzag and armchair edges. We study AA- and AB-(Bernal) stacked BLG QDs and obtain the energy levels in both the absence and the presence of a perpendicular electric field (i.e., biased BLG QDs). Our results show that the size dependence of the energy levels is different from that of monolayer graphene QDs. The energy spectrum of AB-stacked BLG QDs with zigzag edges exhibits edge states which spread out into the opened energy gap in the presence of a perpendicular electric field. We found that the behavior of these edges states is different for the hexagonal and triangular geometries. In the case of AA-stacked BLG QDs, the electron and hole energy levels cross each other in both cases of armchair and zigzag edges as the dot size or the applied bias increases.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 21
DOI: 10.1103/PhysRevB.92.115437
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“Geometry and edge effects on the energy levels of graphene quantum rings : a comparison between tight-binding and simplified Dirac models”. da Costa DR, Chaves A, Zarenia M, Pereira JM, Farias GA, Peeters FM, Physical review : B : condensed matter and materials physics 89, 075418 (2014). http://doi.org/10.1103/PhysRevB.89.075418
Abstract: We present a systematic study of the energy spectra of graphene quantum rings having different geometries and edge types in the presence of a perpendicular magnetic field. Results are obtained within the tight-binding (TB) and Dirac models and we discuss which features of the former can be recovered by using the approximations imposed by the latter. Energy levels of graphene quantum rings obtained by diagonalizing the TB Hamiltonian are demonstrated to be strongly dependent on the rings geometry and the microscopical structure of the edges. This makes it difficult to recover those spectra by the existing theories that are based on the continuum (Dirac) model. Nevertheless, our results show that both approaches (i.e., TB and Dirac model) may provide similar results, but only for very specific combinations of ring geometry and edge types. The results obtained by a simplified model describing an infinitely thin circular Dirac ring show good agreement with those obtained for hexagonal and rhombus armchair graphene rings within the TB model. Moreover, we show that the energy levels of a circular quantum ring with an infinite mass boundary condition obtained within the Dirac model agree with those for a ring defined by a ring-shaped staggered potential obtained within the TB model.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 56
DOI: 10.1103/PhysRevB.89.075418
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“Wave-packet dynamics and valley filter in strained graphene”. Chaves A, Covaci L, Rakhimov KY, Farias GA, Peeters FM, Physical review : B : condensed matter and materials physics 82, 205430 (2010). http://doi.org/10.1103/PhysRevB.82.205430
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.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 95
DOI: 10.1103/PhysRevB.82.205430
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“Lowering of the spatial symmetry at the gamma ->alpha phase transition in cerium”. Tsvyashchenko AV, Nikolaev AV, Velichkov AI, Salamatin AV, Fomicheva LN, Ryasny GK, Sorokin AA, Kochetov OI, Budzynski M, Michel KH, Physical review : B : condensed matter and materials physics 82, 1 (2010). http://doi.org/10.1103/PhysRevB.82.092102
Abstract: Using time-differential perturbed angular correlation spectroscopy we have measured the electric field gradient (EFG) at 111Cd probe nuclei in solid Ce in a pressure range up to 8 GPa. Covering various allotropic phases of Ce, we find that the value of the EFG in the cubic α phase is almost four times larger than in the cubic γ phase and close to values in the noncubic phases α′ and α″. These results together with the differences in time modulation of the spectra are interpreted as evidence for quadrupolar electronic charge-density ordering and symmetry lowering at the γ→α transition while the lattice remains face-centered cubic
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 11
DOI: 10.1103/PhysRevB.82.092102
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“Graphene-based heterostructures with moire superlattice that preserve the Dirac cone: a first-principles study”. Kong X, Li L, Peeters FM, Journal of physics : condensed matter 31, 255302 (2019). http://doi.org/10.1088/1361-648X/AB132F
Abstract: In van der Waals heterostructures consisting of graphene and a substrate, lattice mismatch often leads to a moire pattern with a huge supercell, preventing its treatment within first- principles calculations. Previous theoretical works considered mostly simple stacking models such as AB, AA with straining the lattice of graphene to match that of the substrate. Here, we propose a moire superlattice build from graphene and porous graphene or graphyne like monolayers, having a lower interlayer binding energy, needing little strain in order to match the lattices. In contrast to the results from the simple stacking models, the present ab initio calculations for the moire superlattices show different properties in lattice structure, energy, and band structures. For example, the Dirac cone at the K point is preserved and a linear energy dispersion near the Fermi level is obtained.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.649
Times cited: 5
DOI: 10.1088/1361-648X/AB132F
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“Tunable 2D-gallium arsenide and graphene bandgaps in a graphene/GaAs heterostructure : an ab initio study”. Gonzalez-Garcia A, Lopez-Perez W, Gonzalez-Hernandez R, Rodriguez JA, Milošević, MV, Peeters FM, Journal of physics : condensed matter 31, 265502 (2019). http://doi.org/10.1088/1361-648X/AB0D70
Abstract: The bandgap behavior of 2D-GaAs and graphene have been investigated with van der Waals heterostructured into a yet unexplored graphene/GaAs bilayer, under both uniaxial stress along c axis and different planar strain distributions. The 2D-GaAs bandgap nature changes from Gamma-K indirect in isolated monolayer to Gamma-Gamma direct in graphene/GaAs bilayer. In the latter, graphene exhibits a bandgap of 5 meV. The uniaxial stress strongly affects the graphene electronic bandgap, while symmetric in-plane strain does not open the bandgap in graphene. Nevertheless, it induces remarkable changes on the GaAs bandgap-width around the Fermi level. However, when applying asymmetric in-plane strain to graphene/GaAs, the graphene sublattice symmetry is broken, and the graphene bandgap is open at the Fermi level to a maximum width of 814 meV. This value is much higher than that reported for just graphene under asymmetric strain. The Gamma-Gamma direct bandgap of GaAs remains unchanged in graphene/ GaAs under different types of applied strain. The analyses of phonon dispersion and the elastic constants yield the dynamical and mechanical stability of the graphene/GaAs system, respectively. The calculated mechanical properties for bilayer heterostructure are better than those of their constituent monolayers. This finding, together with the tunable graphene bandgap not only by the strength but also by the direction of the strain, enhance the potential for strain engineering of ultrathin group-III-V electronic devices hybridized by graphene.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.649
Times cited: 10
DOI: 10.1088/1361-648X/AB0D70
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“Two-dimensional hydrogenated buckled gallium arsenide: an ab initio study”. Gonzalez-Garcia A, Lopez-Perez W, Gonzalez-Hernandez R, Rivera-Julio J, Espejo C, Milošević, MV, Peeters FM, Journal Of Physics-Condensed Matter 32, 145502 (2020). http://doi.org/10.1088/1361-648X/AB6043
Abstract: First-principles calculations have been carried out to investigate the stability, structural and electronic properties of two-dimensional (2D) hydrogenated GaAs with three possible geometries: chair, zigzag-line and boat configurations. The effect of van der Waals interactions on 2D H-GaAs systems has also been studied. These configurations were found to be energetic and dynamic stable, as well as having a semiconducting character. Although 2D GaAs adsorbed with H tends to form a zigzag-line configuration, the energy differences between chair, zigzag-line and boat are very small which implies the metastability of the system. Chair and boat configurations display a – direct bandgap nature, while pristine 2D-GaAs and zigzag-line are indirect semiconductors. The bandgap sizes of all configurations are also hydrogen dependent, and wider than that of pristine 2D-GaAs with both PBE and HSE functionals. Even though DFT-vdW interactions increase the adsorption energies and reduce the equilibrium distances of H-GaAs systems, it presents, qualitatively, the same physical results on the stability and electronic properties of our studied systems with PBE functional. According to our results, 2D buckled gallium arsenide is a good candidate to be synthesized by hydrogen surface passivation as its group III-V partners 2D buckled gallium nitride and boron nitride. The hydrogenation of 2D-GaAs tunes the bandgap of pristine 2D-GaAs, which makes it a potential candidate for optoelectronic applications in the blue and violet ranges of the visible electromagnetic spectrum.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.7
Times cited: 2
DOI: 10.1088/1361-648X/AB6043
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“Predicted field-dependent increase of critical currents in asymmetric superconducting nanocircuits”. Clem JR, Mawatari Y, Berdiyorov GR, Peeters FM, Physical review : B : condensed matter and materials physics 85, 144511 (2012). http://doi.org/10.1103/PhysRevB.85.144511
Abstract: The critical current of a thin superconducting strip of width W much larger than the Ginzburg-Landau coherence length xi but much smaller than the Pearl length Lambda = 2 lambda(2)/d is maximized when the strip is straight with defect-free edges. When a perpendicular magnetic field is applied to a long straight strip, the critical current initially decreases linearly with H but then decreases more slowly with H when vortices or antivortices are forced into the strip. However, in a superconducting strip containing sharp 90 degrees or 180 degrees turns, the zero-field critical current at H = 0 is reduced because vortices or antivortices are preferentially nucleated at the inner corners of the turns, where current crowding occurs. Using both analytic London-model calculations and time-dependent Ginzburg-Landau simulations, we predict that in such asymmetric strips the resulting critical current can be increased by applying a perpendicular magnetic field that induces a current-density contribution opposing the applied current density at the inner corners. This effect should apply to all turns that bend in the same direction.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 40
DOI: 10.1103/PhysRevB.85.144511
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“Fluctuations in superconducting rings with two order parameters”. Berger J, Milošević, MV, Physical review : B : condensed matter and materials physics 84, 214515 (2011). http://doi.org/10.1103/PhysRevB.84.214515
Abstract: Motivated by two-band superconductivity in, e.g., borides and pnictides, starting from the two-band Ginzburg-Landau energy functional, we discuss how the presence of two order parameters and the coupling between them influence a superconducting ring in the fluctuative regime. Our method is an extension of the von OppenRiedel formalism for rings; it is exact, but requires numerical implementation. We also study approximations for which analytic expressions can be obtained, and check their ranges of validity. We provide estimates for the temperature ranges where fluctuations are important, calculate the persistent current in MgB2 rings as a function of temperature and enclosed flux, and point out its additional dependence on the cross-section area of the wire from which the ring is made. We find temperature regions in which fluctuations enhance the persistent currents and regions where they inhibit the persistent current. The presence of two order parameters that can fluctuate independently always leads to larger averages of the order parameters at Tc, but yields larger persistent current only for appropriate parameters. In cases of very different material parameters for the two coupled condensates, the persistent current is inhibited.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 7
DOI: 10.1103/PhysRevB.84.214515
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“Application of optical beams to electrons in graphene”. Matulis A, Masir MR, Peeters FM, Physical review : B : condensed matter and materials physics 83, 115458 (2011). http://doi.org/10.1103/PhysRevB.83.115458
Abstract: The technique of beam optics is applied to the description of the wave function of Dirac electrons. This approach is illustrated by considering electron transmission through simple nonhomogeneous structures, such as flat and bent p-n junctions and superlattices. We found that a convex p-n junction compresses the beam waist, while a concave interface widens it without loosing its focusing properties. At a flat p-n junction the waist of the transmitted Gaussian beam can be narrowed or widened, depending on the angle of incidence. A general condition is derived for the occurrence of beam collimation in a superlattice which is less stringent than previous discussed.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 13
DOI: 10.1103/PhysRevB.83.115458
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“Quantum effects in a free-standing graphene lattice : path-integral against classical Monte Carlo simulations”. Brito BGA, Candido L, Hai G-Q, Peeters FM, Physical review : B : condensed matter and materials physics 92, 195416 (2015). http://doi.org/10.1103/PhysRevB.92.195416
Abstract: In order to study quantum effects in a two-dimensional crystal lattice of a free-standing monolayer graphene, we have performed both path-integral Monte Carlo (PIMC) and classical Monte Carlo (MC) simulations for temperatures up to 2000 K. The REBO potential is used for the interatomic interaction. The total energy, interatomic distance, root-mean-square displacement of the atom vibrations, and the free energy of the graphene layer are calculated. The obtained lattice vibrational energy per atom from the classical MC simulation is very close to the energy of a three-dimensional harmonic oscillator 3k(B)T. The PIMC simulation shows that quantum effects due to zero-point vibrations are significant for temperatures T < 1000 K. The quantum contribution to the lattice vibrational energy becomes larger than that of the classical lattice for T < 400 K. The lattice expansion due to the zero-point motion causes an increase of 0.53% in the lattice parameter. A minimum in the lattice parameter appears at T similar or equal to 500 K. Quantum effects on the atomic vibration amplitude of the graphene lattice and its free energy are investigated.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 22
DOI: 10.1103/PhysRevB.92.195416
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“Substrate-induced proximity effect in superconducting niobium nanofilms”. Rezvani SJ, Perali A, Fretto M, De Leo N, Flammia L, Milošević, M, Nannarone S, Pinto N, Condensed Matter 4, 4 (2018). http://doi.org/10.3390/CONDMAT4010004
Abstract: Structural and superconducting properties of high-quality niobium nanofilms with different thicknesses are investigated on silicon oxide (SiO2) and sapphire substrates. The role played by the different substrates and the superconducting properties of the Nb films are discussed based on the defectivity of the films and on the presence of an interfacial oxide layer between the Nb film and the substrate. The X-ray absorption spectroscopy is employed to uncover the structure of the interfacial layer. We show that this interfacial layer leads to a strong proximity effect, especially in films deposited on a SiO2 substrate, altering the superconducting properties of the Nb films. Our results establish that the critical temperature is determined by an interplay between quantum-size effects, due to the reduction of the Nb film thicknesses, and proximity effects. The detailed investigation here provides reference characterizations and has direct and important implications for the fabrication of superconducting devices based on Nb nanofilms.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Times cited: 3
DOI: 10.3390/CONDMAT4010004
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“Vortex patterns in a mesoscopic superconducting rod with a magnetic dot”. Doria MM, Romaguera AR de C, Peeters FM, Physical review : B : condensed matter and materials physics 81, 104529 (2010). http://doi.org/10.1103/PhysRevB.81.104529
Abstract: We study a mesoscopic superconducting rod with a magnetic dot on its top having its moment oriented along the axis of symmetry. We study the dependence of the vortex pattern with the height and find that for very short and very long rods, the vortex pattern acquires a simple structure, consisting of giant and of multivortex states, respectively. In the long limit, the most stable configuration consists of two vortices, that reach the lateral surface of the rod diametrically opposed. The long rod shows reentrant behavior within some range of its radius and of the dots magnetic moment. Our results are obtained within the Ginzburg-Landau approach in the limit of no magnetic shielding.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 5
DOI: 10.1103/PhysRevB.81.104529
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“Electron polarization function and plasmons in metallic armchair graphene nanoribbons”. Shylau AA, Badalyan SM, Peeters FM, Jauho AP, Physical review : B : condensed matter and materials physics 91, 205444 (2015). http://doi.org/10.1103/PhysRevB.91.205444
Abstract: Plasmon excitations in metallic armchair graphene nanoribbons are investigated using the random phase approximation. An exact analytical expression for the polarization function of Dirac fermions is obtained, valid for arbitrary temperature and doping. We find that at finite temperatures, due to the phase space redistribution among inter-band and intra-band electronic transitions in the conduction and valence bands, the full polarization function becomes independent of temperature and position of the chemical potential. It is shown that for a given width of nanoribbon there exists a single plasmon mode whose energy dispersion is determined by the graphene's fine structure constant. In the case of two Coulomb-coupled nanoribbons, this plasmon splits into in-phase and out-of-phase plasmon modes with splitting energy determined by the inter-ribbon spacing.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 13
DOI: 10.1103/PhysRevB.91.205444
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“G0W0 band gap of ZnO : effects of plasmon-pole models”. Stankovski M, Antonius G, Waroquiers D, Miglio A, Dixit H, Sankaran K, Giantomassi M, Gonze X, Côté, M, Rignanese G-M, Physical review : B : condensed matter and materials physics 84, 241201 (2011). http://doi.org/10.1103/PhysRevB.84.241201
Abstract: Carefully converged calculations are performed for the band gap of ZnO within many-body perturbation theory (G0W0 approximation). The results obtained using four different well-established plasmon-pole models are compared with those of explicit calculations without such models (the contour-deformation approach). This comparison shows that, surprisingly, plasmon-pole models depending on the f-sum rule gives less precise results. In particular, it confirms that the band gap of ZnO is underestimated in the G0W0 approach as compared to experiment, contrary to the recent claim of Shih et al. [ Phys. Rev. Lett. 105 146401 (2010)].
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 81
DOI: 10.1103/PhysRevB.84.241201
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“Gapless interface states at the junction between two topological insulators”. De Beule C, Partoens B, Physical review : B : condensed matter and materials physics 87, 115113 (2013). http://doi.org/10.1103/PhysRevB.87.115113
Abstract: We consider a junction between two topological insulators and calculate the properties of the interface states with an effective low-energy Hamiltonian for topological insulators with a single cone on the surface. This system bears a close resemblance to bilayer graphene, as both result from the hybridization of Dirac cones. We find gapless interface states not only when the helicity directions of the topological surface states are oppositely oriented, but they can also exist if they are equally oriented. Furthermore, we find that the existence of the interface states can be understood from the closing of the bulk gap when the helicity changes orientation. Recently superluminal tachyonic excitations were also claimed to exist at the interface between topological insulators. However, here we show that these interface states do not exist. DOI: 10.1103/PhysRevB.87.115113
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 8
DOI: 10.1103/PhysRevB.87.115113
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“Thermodynamic properties of the electron gas in multilayer graphene in the presence of a perpendicular magnetic field”. Van Duppen B, Peeters FM, Physical review : B : condensed matter and materials physics 88, 245429 (2013). http://doi.org/10.1103/PhysRevB.88.245429
Abstract: The thermodynamic properties of the electron gas in multilayer graphene depend strongly on the number of layers and the type of stacking. Here we analyze how those properties change when we vary the number of layers for rhombohedral stacked multilayer graphene and compare our results with those from a conventional two-dimensional electron gas. We show that the highly degenerate zero-energy Landau level which is partly filled with electrons and partly with holes has a strong influence on the values of the different thermodynamic quantities.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 2
DOI: 10.1103/PhysRevB.88.245429
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“Interplay between lattice dynamics and superconductivity in Nb3Sn thin films”. Couet S, Peelaers H, Trekels M, Houben K, Petermann C, Hu MY, Zhao JY, Bi W, Alp EE, Menéndez E, Partoens B, Peeters FM, Van Bael MJ, Vantomme A, Temst K;, Physical review : B : condensed matter and materials physics 88, 045437 (2013). http://doi.org/10.1103/PhysRevB.88.045437
Abstract: We investigate the link between superconductivity and atomic vibrations in Nb3Sn films with a thickness ranging from 10 to 50 nm. The challenge of measuring the phonon density of states (PDOS) of these films has been tackled by employing the technique of nuclear inelastic scattering by Sn-119 isotopes to reveal the Sn-partial phonon density of states. With the support of ab initio calculations, we evaluate the effect of reduced film thickness on the PDOS. This approach allows us to estimate the changes in superconducting critical temperature T-c induced by phonon confinement, which turned out to be limited to a few tenths of K. The presented method is successful for the Nb3Sn system and paves the way for more systematic studies of the role of phonon confinement in Sn-containing superconductors.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 5
DOI: 10.1103/PhysRevB.88.045437
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“Strain-induced band gaps in bilayer graphene”. Verberck B, Partoens B, Peeters FM, Trauzettel B, Physical review : B : condensed matter and materials physics 85, 125403 (2012). http://doi.org/10.1103/PhysRevB.85.125403
Abstract: We present a tight-binding investigation of strained bilayer graphene within linear elasticity theory, focusing on the different environments experienced by the A and B carbon atoms of the different sublattices. We find that the inequivalence of the A and B atoms is enhanced by the application of perpendicular strain epsilon(zz), which provides a physical mechanism for opening a band gap, most effectively obtained when pulling the two graphene layers apart. In addition, perpendicular strain introduces electron-hole asymmetry and can result in linear electronic dispersion near the K point. Our findings suggest experimental means for strain-engineered band gaps in bilayer graphene.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 53
DOI: 10.1103/PhysRevB.85.125403
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