|
“Real-time measurement of the emergence of superconducting order in a high-temperature superconductor”. Madan I, Kusar P, Baranov VV, Lu-Dac M, Kabanov VV, Mertelj T, Mihailovic D, Physical review B 93, 224520 (2016). http://doi.org/10.1103/PHYSREVB.93.224520
Abstract: Systems which rapidly evolve through symmetry-breaking transitions on timescales comparable to the fluctuation timescale of the single-particle excitations may behave very differently than under controlled near-ergodic conditions. A real-time investigation with high temporal resolution may reveal insights into the ordering through the transition that are not available in static experiments. We present an investigation of the system trajectory through a normal-to-superconductor transition in a prototype high-temperature superconducting cuprate in which such a situation occurs. Using a multiple pulse femtosecond spectroscopy technique we measure the system trajectory and time evolution of the single-particle excitations through the transition in La1.9Sr0.1CuO4 and compare the data to a simulation based on the time-dependent Ginzburg-Landau theory, using the laser excitation fluence as an adjustable parameter controlling the quench conditions in both experiment and theory. The comparison reveals the presence of significant superconducting fluctuations which precede the transition on short timescales. By including superconducting fluctuations as a seed for the growth of the superconducting order we can obtain a satisfactory agreement of the theory with the experiment. Remarkably, the pseudogap excitations apparently play no role in this process.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 5
DOI: 10.1103/PHYSREVB.93.224520
|
|
|
“Skyrmionic vortex lattices in coherently coupled three-component Bose-Einstein condensates”. Orlova NV, Kuopanportti P, Milošević, MV, Physical Review A 94, 023617 (2016). http://doi.org/10.1103/PHYSREVA.94.023617
Abstract: We show numerically that a harmonically trapped and coherently Rabi-coupled three-component Bose-Einstein condensate can host unconventional vortex lattices in its rotating ground state. The discovered lattices incorporate square and zig-zag patterns, vortex dimers and chains, and doubly quantized vortices, and they can be quantitatively classified in terms of a skyrmionic topological index, which takes into account the multicomponent nature of the system. The exotic ground-state lattices arise due to the intricate interplay of the repulsive density-density interactions and the Rabi couplings as well as the ubiquitous phase frustration between the components. In the frustrated state, domain walls in the relative phases can persist between some components even at strong Rabi coupling, while vanishing between others. Consequently, in this limit the three-component condensate effectively approaches a two-component condensate with only density-density interactions. At intermediate Rabi coupling strengths, however, we face unique vortex physics that occurs neither in the two-component counterpart nor in the purely density-density-coupled three-component system.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.925
Times cited: 16
DOI: 10.1103/PHYSREVA.94.023617
|
|
|
“Stress dependence of the suspended graphene work function : vacuum Kelvin probe force microscopy and density functional theory”. Volodin A, Van Haesendonck C, Leenaerts O, Partoens B, Peeters FM, Applied physics letters 110, 193101 (2017). http://doi.org/10.1063/1.4982931
Abstract: We report on work function measurements on graphene, which is exfoliated over a predefined array of wells in silicon oxide, by Kelvin probe force microscopy operating in a vacuum. The obtained graphene sealed microchambers can support large pressure differences, providing controllable stretching of the nearly impermeable graphene membranes. These measurements allow detecting variations of the work function induced by the mechanical stresses in the suspended graphene where the work function varies linearly with the strain and changes by 62 +/- 2 meV for 1 percent of strain. Our related ab initio calculations result in a work function variation that is a factor of 1.4 larger than the experimental value. The limited discrepancy between the theory and the experiment can be accounted for by a charge transfer from the unstrained to the strained graphene regions. Published by AIP Publishing.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.411
Times cited: 8
DOI: 10.1063/1.4982931
|
|
|
“Effect of straining graphene on nanopore creation using Si cluster bombardment: A reactive atomistic investigation”. Berdiyorov GR, Mortazavi B, Ahzi S, Peeters FM, Khraisheh MK, Journal of applied physics 120, 225108 (2016). http://doi.org/10.1063/1.4971767
Abstract: Graphene nanosheets have recently received a revival of interest as a new class of ultrathin, high-flux, and energy-efficient sieving membranes because of their unique two-dimensional and atomically thin structure, good flexibility, and outstanding mechanical properties. However, for practical applications of graphene for advanced water purification and desalination technologies, the creation of well controlled, high-density, and subnanometer diameter pores becomes a key factor. Here, we conduct reactive force-field molecular dynamics simulations to study the effect of external strain on nanopore creation in the suspended graphene by bombardment with Si clusters. Depending on the size and energy of the clusters, different kinds of topography were observed in the graphene sheet. In all the considered conditions, tensile strain results in the creation of nanopores with regular shape and smooth edges. On the contrary, compressive strain increases the elastic response of graphene to irradiation that leads to the formation of net-like defective structures with predominantly carbon atom chains. Our findings show the possibility of creating controlled nanopores in strained graphene by bombardment with Si clusters. Published by AIP Publishing.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.068
Times cited: 10
DOI: 10.1063/1.4971767
|
|
|
“Superconductivity between standard types: Multiband versus single-band materials”. Vagov A, Shanenko AA, Milošević, MV, Axt VM, Vinokur VM, Aguiar JA, Peeters FM, Physical review B 93, 174503 (2016). http://doi.org/10.1103/PhysRevB.93.174503
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 37
DOI: 10.1103/PhysRevB.93.174503
|
|
|
“Excitons and trions in monolayer transition metal dichalcogenides : a comparative study between the multiband model and the quadratic single-band model”. Van der Donck M, Zarenia M, Peeters FM, Physical review B 96, 035131 (2017). http://doi.org/10.1103/PHYSREVB.96.035131
Abstract: The electronic and structural properties of excitons and trions in monolayer transition metal dichalcogenides are investigated using both a multiband and a single- band model. In the multiband model we construct the excitonic Hamiltonian in the product base of the single-particle states at the conduction and valence band edges. We decouple the corresponding energy eigenvalue equation and solve the resulting differential equation self-consistently, using the finite element method (FEM), to determine the energy eigenvalues and the wave functions. As a comparison, we also consider the simple single-band model which is often used in numerical studies. We solve the energy eigenvalue equation using the FEM as well as with the stochastic variational method (SVM) in which a variational wave function is expanded in a basis of a large number of correlated Gaussians. We find good agreement between the results of both methods, as well as with other theoretical works for excitons, and we also compare with available experimental data. For trions the agreement between both methods is not as good due to our neglect of angular correlations when using the FEM. Finally, when comparing the two models, we see that the presence of the valence bands in the mutiband model leads to differences with the single- band model when (interband) interactions are strong.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 50
DOI: 10.1103/PHYSREVB.96.035131
|
|
|
“Gate induced monolayer behavior in twisted bilayer black phosphorus”. Sevik C, Wallbank JR, Gulseren O, Peeters FM, Çakir D, 2D materials 4, 035025 (2017). http://doi.org/10.1088/2053-1583/AA80C4
Abstract: Optical and electronic properties of black phosphorus strongly depend on the number of layers and type of stacking. Using first-principles calculations within the framework of density functional theory, we investigate the electronic properties of bilayer black phosphorus with an interlayer twist angle of 90 degrees. These calculations are complemented with a simple (k) over right arrow . (p) over right arrow model which is able to capture most of the low energy features and is valid for arbitrary twist angles. The electronic spectrum of 90 degrees twisted bilayer black phosphorus is found to be x-y isotropic in contrast to the monolayer. However x-y anisotropy, and a partial return to monolayer-like behavior, particularly in the valence band, can be induced by an external out-of-plane electric field. Moreover, the preferred hole effective mass can be rotated by 90 degrees simply by changing the direction of the applied electric field. In particular, a +0.4 (-0.4) V angstrom(1) out-of-plane electric field results in a similar to 60% increase in the hole effective mass along the y (x) axis and enhances the m(y)*/m(x)* (m(x)*/m(y)*) ratio as much as by a factor of 40. Our DFT and (k) over right arrow . (p) over right arrow simulations clearly indicate that the twist angle in combination with an appropriate gate voltage is a novel way to tune the electronic and optical properties of bilayer phosphorus and it gives us a new degree of freedom to engineer the properties of black phosphorus based devices.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 6.937
Times cited: 13
DOI: 10.1088/2053-1583/AA80C4
|
|
|
“Graphene membrane as a pressure gauge”. Milovanović, SP, Tadic MZ, Peeters FM, Applied physics letters 111, 043101 (2017). http://doi.org/10.1063/1.4995983
Abstract: Straining graphene results in the appearance of a pseudo-magnetic field which alters its local electronic properties. Applying a pressure difference between the two sides of the membrane causes it to bend/bulge resulting in a resistance change. We find that the resistance changes linearly with pressure for bubbles of small radius while the response becomes non-linear for bubbles that stretch almost to the edges of the sample. This is explained as due to the strong interference of propagating electronic modes inside the bubble. Our calculations show that high gauge factors can be obtained in this way which makes graphene a good candidate for pressure sensing. Published by AIP Publishing.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.411
Times cited: 11
DOI: 10.1063/1.4995983
|
|
|
“New group-V elemental bilayers : a tunable structure model with four-, six-, and eight-atom rings”. Kong X, Li L, Leenaerts O, Liu X-J, Peeters FM, Physical review B 96, 035123 (2017). http://doi.org/10.1103/PHYSREVB.96.035123
Abstract: Two-dimensional group-V elemental materials have attracted widespread attention due to their nonzero band gap while displaying high electron mobility. Using first-principles calculations, we propose a series of new elemental bilayers with group-V elements (Bi, Sb, As). Our study reveals the dynamical stability of four-, six-, and eight-atom ring structures, demonstrating their possible coexistence in such bilayer systems. The proposed structures for Sb and As are large-gap semiconductors that are potentially interesting for applications in future nanodevices. The Bi structures have nontrivial topological properties with a direct nontrivial band gap. The nontrivial gap is shown to arise from a band inversion at the Brillouin zone center due to the strong intrinsic spin-orbit coupling in Bi atoms. Moreover, we demonstrate the possibility of tuning the properties of these materials by enhancing the ratio of six-atom rings to four-and eight-atom rings, which results in wider nontrivial band gaps and lower formation energies.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 14
DOI: 10.1103/PHYSREVB.96.035123
|
|
|
“Self-assembly of rigid magnetic rods consisting of single dipolar beads in two dimensions”. Domingos JLC, Peeters FM, Ferreira WP, Physical review E 96, 012603 (2017). http://doi.org/10.1103/PHYSREVE.96.012603
Abstract: Molecular dynamics simulations are used to investigate the structural properties of a two-dimensional ensemble of magnetic rods, which are modeled as aligned single dipolar beads. The obtained self-assembled configurations can be characterized as (1) clusters, (2) percolated, and (3) ordered structures, and their structural properties are investigated in detail. By increasing the aspect ratio of the magnetic rods, we show that the percolation transition is suppressed due to the reduced mobility of the rods in two dimensions. Such a behavior is opposite to the one observed in three dimensions. A magnetic bulk phase is found with local ferromagnetic order and an unusual nonmonotonic behavior of the nematic order is observed.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.366
Times cited: 8
DOI: 10.1103/PHYSREVE.96.012603
|
|
|
“Spatial design and control of graphene flake motion”. Ghorbanfekr-Kalashami H, Peeters FM, Novoselov KS, Neek-Amal M, Physical review B 96, 060101 (2017). http://doi.org/10.1103/PHYSREVB.96.060101
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 3
DOI: 10.1103/PHYSREVB.96.060101
|
|
|
“Anisotropic hybrid excitation modes in monolayer and double-layer phosphorene on polar substrates”. Saberi-Pouya S, Vazifehshenas T, Salavati-fard T, Farmanbar M, Physical review B 96, 115402 (2017). http://doi.org/10.1103/PHYSREVB.96.115402
Abstract: We investigate the anisotropic hybrid surface optical (SO) phonon-plasmon dispersion relations in monolayer and double-layer phosphorene systems located on the polar substrates, such as SiO2, h-BN, and Al2O3. We calculate these hybrid modes by using the dynamical dielectric function in the random phase approximation in which the electron-electron interaction and long-range electric field generated by the substrate SO phonons via Frohlich interaction are taken into account. In the long-wavelength limit, we obtain some analytical expressions for the hybrid SO phonon-plasmon dispersion relations which agree with those obtained from the loss function. Our results indicate a strong anisotropy in SO phonon-plasmon modes, which are stronger along the light-mass direction in our heterostructures. Furthermore, we find that the type of substrate has a significant effect on the dispersion relations of the coupled modes. Importantly, the hybrid excitations are apparently sensitive to the misalignment and separation between layers in double-layer phosphorene.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 6
DOI: 10.1103/PHYSREVB.96.115402
|
|
|
“Double quantum dots defined in bilayer graphene”. Zebrowski DP, Peeters FM, Szafran B, Physical review B 96, 035434 (2017). http://doi.org/10.1103/PHYSREVB.96.035434
Abstract: Artificial molecular states of double quantum dots defined in bilayer graphene are studied with the atomistic tight-binding method and its low-energy continuum approximation. We indicate that the extended electron wave functions have opposite parities on sublattices of the layers and that the ground-state wave-function components change from bonding to antibonding with the interdot distance. In the weak-coupling limit, the one most relevant for quantum dots defined electrostatically, the signatures of the interdot coupling include, for the two-electron ground state, formation of states with symmetric or antisymmetric spatial wave functions split by the exchange energy. In the high-energy part of the spectrum the states with both electrons in the same dot are found with the splitting of energy levels corresponding to simultaneous tunneling of the electron pair from one dot to the other.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 6
DOI: 10.1103/PHYSREVB.96.035434
|
|
|
“Evolution of multigap superconductivity in the atomically thin limit : strain-enhanced three-gap superconductivity in monolayer MgB2”. Bekaert J, Aperis A, Partoens B, Oppeneer PM, Milošević, MV, Physical review B 96, 094510 (2017). http://doi.org/10.1103/PHYSREVB.96.094510
Abstract: Starting from first principles, we show the formation and evolution of superconducting gaps in MgB2 at its ultrathin limit. Atomically thin MgB2 is distinctly different from bulk MgB2 in that surface states become comparable in electronic density to the bulklike sigma and pi bands. Combining the ab initio electron-phonon coupling with the anisotropic Eliashberg equations, we showthat monolayer MgB2 develops three distinct superconducting gaps, on completely separate parts of the Fermi surface due to the emergent surface contribution. These gaps hybridize nontrivially with every extra monolayer added to the film owing to the opening of additional coupling channels. Furthermore, we reveal that the three-gap superconductivity in monolayer MgB2 is robust over the entire temperature range that stretches up to a considerably high critical temperature of 20 K. The latter can be boosted to >50K under biaxial tensile strain of similar to 4%, which is an enhancement that is stronger than in any other graphene-related superconductor known to date.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 56
DOI: 10.1103/PHYSREVB.96.094510
|
|
|
“Multicomponent plasmons in monolayer MoS2 with circularly polarized optical pumping”. Xiao YM, Xu W, Peeters FM, Van Duppen B, Physical review B 96, 085405 (2017). http://doi.org/10.1103/PHYSREVB.96.085405
Abstract: By making use of circularly polarized light and electrostatic gating, monolayer molybdenum disulfide (ML – MoS2) can form a platform supporting multiple types of charge carriers. They can be discriminated by their spin, valley index, or whether they are electrons or holes. We investigate the collective properties of those charge carriers and are able to identify distinct plasmon modes. We analyze the corresponding dispersion relation, lifetime, and oscillator strength, and calculate the phase relation between the oscillations in the different components of the plasmon modes. All platforms in ML-MoS2 support a long-wavelength root q plasmon branch at zero kelvins. In addition to this, for an n-component system, n-1 distinct plasmon modes appear as acoustic modes with linear dispersion in the long-wavelength limit. These modes correspond to out-of-phase oscillations in the different fermion liquids and have, although being damped, a relatively long lifetime. Additionally, we also find distinct modes at large wave vectors that are more strongly damped by intraband processes.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 2
DOI: 10.1103/PHYSREVB.96.085405
|
|
|
“Sound waves and flexural mode dynamics in two-dimensional crystals”. Michel KH, Scuracchio P, Peeters FM, Physical review B 96, 094302 (2017). http://doi.org/10.1103/PHYSREVB.96.094302
Abstract: Starting from a Hamiltonian with anharmonic coupling between in-plane acoustic displacements and outof-plane (flexural) modes, we derived coupled equations of motion for in-plane displacements correlations and flexural mode density fluctuations. Linear response theory and time-dependent thermal Green's functions techniques are applied in order to obtain different response functions. As external perturbations we allow for stresses and thermal heat sources. The displacement correlations are described by a Dyson equation where the flexural density distribution enters as an additional perturbation. The flexural density distribution satisfies a kinetic equation where the in-plane lattice displacements act as a perturbation. In the hydrodynamic limit this system of coupled equations is at the basis of a unified description of elastic and thermal phenomena, such as isothermal versus adiabatic sound motion and thermal conductivity versus second sound. The general theory is formulated in view of application to graphene, two-dimensional h-BN, and 2H-transition metal dichalcogenides and oxides.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 6
DOI: 10.1103/PHYSREVB.96.094302
|
|
|
“Strong anisotropic optical conductivity in two-dimensional puckered structures : the role of the Rashba effect”. Saberi-Pouya S, Vazifehshenas T, Salavati-Fard T, Farmanbar M, Peeters FM, Physical review B 96, 075411 (2017). http://doi.org/10.1103/PHYSREVB.96.075411
Abstract: within the Kubo formalism. We show that the anisotropic Rashba effect caused by an external field significantly changes the magnitude of the spin splitting. Furthermore, we obtain an analytical expression for the longitudinal optical conductivity associated with interband transitions as a function of the frequency for arbitrary polarization angle. We find that the diagonal components of the optical conductivity tensor are direction dependent and the optical absorption spectrum exhibits a strongly anisotropic absorption window. The height and width of this absorption window are very sensitive to the anisotropy of the system. While the height of absorption peak increases with increasing effective mass anisotropy ratio, the peak intensity is larger when the light polarization is along the armchair direction. Moreover, the absorption peak width becomes broader as the density-of-states mass or Rashba interaction is enhanced. These features in the optical absorption spectrum can be used to determine parameters relevant for spintronics.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 16
DOI: 10.1103/PHYSREVB.96.075411
|
|
|
“Tight-binding model investigation of the biaxial strain induced topological phase transition in GeCH3”. Rezaei M, Sisakht ET, Fazileh F, Aslani Z, Peeters FM, Physical review B 96, 085441 (2017). http://doi.org/10.1103/PHYSREVB.96.085441
Abstract: We propose a tight-binding (TB) model, that includes spin-orbit coupling (SOC), to describe the electronic properties of methyl-substituted germanane (GeCH3). This model gives an electronic spectrum in agreement with first principle results close to the Fermi level. Using the Z(2) formalism, we show that a topological phase transition from a normal insulator (NI) to a quantum spin Hall (QSH) phase occurs at 11.6% biaxial tensile strain. The sensitivity of the electronic properties of this system on strain, in particular its transition to the topological insulating phase, makes it very attractive for applications in strain sensors and other microelectronic applications.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 10
DOI: 10.1103/PHYSREVB.96.085441
|
|
|
“Efficient solution of the Wigner-Liouville equation using a spectral decomposition of the force field”. Van de Put ML, Sorée B, Magnus W, Journal of computational physics 350, 314 (2017). http://doi.org/10.1016/J.JCP.2017.08.059
Abstract: The Wigner-Liouville equation is reformulated using a spectral decomposition of the classical force field instead of the potential energy. The latter is shown to simplify the Wigner-Liouville kernel both conceptually and numerically as the spectral force Wigner-Liouville equation avoids the numerical evaluation of the highly oscillatory Wigner kernel which is nonlocal in both position and momentum. The quantum mechanical evolution is instead governed by a term local in space and non-local in momentum, where the non locality in momentum has only a limited range. An interpretation of the time evolution in terms of two processes is presented; a classical evolution under the influence of the averaged driving field, and a probability-preserving quantum-mechanical generation and annihilation term. Using the inherent stability and reduced complexity, a direct deterministic numerical implementation using Chebyshev and Fourier pseudo-spectral methods is detailed. For the purpose of illustration, we present results for the time evolution of a one-dimensional resonant tunneling diode driven out of equilibrium. (C) 2017 Elsevier Inc. All rights reserved.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.744
Times cited: 5
DOI: 10.1016/J.JCP.2017.08.059
|
|
|
“Electronic properties of bilayer phosphorene quantum dots in the presence of perpendicular electric and magnetic fields”. Li LL, Moldovan D, Xu W, Peeters FM, Physical review B 96, 155425 (2017). http://doi.org/10.1103/PHYSREVB.96.155425
Abstract: Using the tight-binding approach, we investigate the electronic properties of bilayer phosphorene (BLP) quantum dots (QDs) in the presence of perpendicular electric and magnetic fields. Since BLP consists of two coupled phosphorene layers, it is of interest to examine the layer-dependent electronic properties of BLP QDs, such as the electronic distributions over the two layers and the so-produced layer-polarization features, and to see how these properties are affected by the magnetic field and the bias potential. We find that in the absence of a bias potential only edge states are layer polarized while the bulk states are not, and the layer-polarization degree (LPD) of the unbiased edge states increases with increasing magnetic field. However, in the presence of a bias potential both the edge and bulk states are layer polarized, and the LPD of the bulk (edge) states depends strongly (weakly) on the interplay of the bias potential and the interlayer coupling. At high magnetic fields, applying a bias potential renders the bulk electrons in a BLP QD to be mainly distributed over the top or bottom layer, resulting in layer-polarized bulk Landau levels (LLs). In the presence of a large bias potential that can drive a semiconductor-to-semimetal transition in BLP, these bulk LLs exhibit different magnetic-field dependences, i.e., the zeroth LLs exhibit a linearlike dependence on the magnetic field while the other LLs exhibit a square-root-like dependence.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 28
DOI: 10.1103/PHYSREVB.96.155425
|
|
|
“Landau levels in biased graphene structures with monolayer-bilayer interfaces”. Mirzakhani M, Zarenia M, Vasilopoulos P, Ketabi SA, Peeters FM, Physical review B 96, 125430 (2017). http://doi.org/10.1103/PHYSREVB.96.125430
Abstract: The electron energy spectrum in monolayer-bilayer-monolayer and in bilayer-monolayer-bilayer graphene structures is investigated and the effects of a perpendicular magnetic field and electric bias are studied. Different types of monolayer-bilayer interfaces are considered as zigzag (ZZ) or armchair (AC) junctions which modify considerably the bulk Landau levels (LLs) when the spectra are plotted as a function of the center coordinate of the cyclotron orbit. Far away from the two interfaces, one obtains the well-known LLs for extended monolayer or bilayer graphene. The LL structure changes significantly at the two interfaces or junctions where the valley degeneracy is lifted for both types of junctions, especially when the distance between them is approximately equal to the magnetic length. Varying the nonuniform bias and the width of this junction-to-junction region in either structure strongly influence the resulting spectra. Significant differences exist between ZZ and AC junctions in both structures. The densities of states (DOSs) for unbiased structures are symmetric in energy whereas those for biased structures are asymmetric. An external bias creates interface LLs in the gaps between the LLs of the unbiased system in which the DOS can be quite small. Such a pattern of LLs can be probed by scanning tunneling microscopy.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 6
DOI: 10.1103/PHYSREVB.96.125430
|
|
|
“Magnetic properties of bilayer graphene quantum dots in the presence of uniaxial strain”. Nascimento JS, da Costa DR, Zarenia M, Chaves A, Pereira JM Jr, Physical review B 96, 115428 (2017). http://doi.org/10.1103/PHYSREVB.96.115428
Abstract: Using the tight-binding approach coupled with mean-field Hubbard model, we theoretically study the effect of mechanical deformations on the magnetic properties of bilayer graphene (BLG) quantum dots (QDs). Results are obtained for AA-and AB(Bernal)-stacked BLG QDs, considering different geometries (hexagonal, triangular and square shapes) and edge types (armchair and zigzag edges). In the absence of strain, our results show that (i) the magnetization is affected by taking different dot sizes only for hexagonal BLG QDs with zigzag edges, exhibiting different critical Hubbard interactions, and (ii) the magnetization does not depend on the interlayer hopping energies, except for the geometries with zigzag edges and AA stacking. In the presence of in-plane and uniaxial strain, for all geometries we obtain two different magnetization regimes depending on the applied strain amplitude. The appearance of such different regimes is due to the breaking of layer and sublattice symmetries in BLG QDs.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 4
DOI: 10.1103/PHYSREVB.96.115428
|
|
|
“Multifaceted impact of a surface step on superconductivity in atomically thin films”. Zhang L-F, Flammia L, Covaci L, Perali A, Milošević, MV, Physical review B 96, 104509 (2017). http://doi.org/10.1103/PHYSREVB.96.104509
Abstract: Recent experiments show that an atomic step on the surface of atomically thin metallic films can strongly affect electronic transport. Here we reveal multiple and versatile effects that such a surface step can have on superconductivity in ultrathin films. By solving the Bogoliubov-de Gennes equations self-consistently in this regime, where quantum confinement dominates the emergent physics, we show that the electronic structure is profoundly modified on the two sides of the step, as is the spatial distribution of the superconducting order parameter and its dependence on temperature and electronic gating. Furthermore, the surface step changes nontrivially the transport properties both in the proximity-induced superconducting pair correlations and the Josephson effect, depending on the step height. These results offer a new route to tailor superconducting circuits and design atomically thin heterojunctions made of one same material.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 7
DOI: 10.1103/PHYSREVB.96.104509
|
|
|
“Normal and skewed phosphorene nanoribbons in combined magnetic and electric fields”. Arsoski VV, Grujić, MM, Čukarić, NA, Tadic MZ, Peeters FM, Physical review B 96, 125434 (2017). http://doi.org/10.1103/PHYSREVB.96.125434
Abstract: The energy spectrum and eigenstates of single-layer black phosphorus nanoribbons in the presence of a perpendicular magnetic field and an in-plane transverse electric field are investigated by means of a tight-binding method, and the effect of different types of edges is examined analytically. A description based on a continuum model is proposed using an expansion of the tight-binding model in the long-wavelength limit. Thewave functions corresponding to the flatband part of the spectrum are obtained analytically and are shown to agree well with the numerical results from the tight-binding method for both narrow (10 nm) and wide (100 nm) nanoribbons. Analytical expressions for the critical magnetic field at which Landau levels are formed and the ranges of wave numbers in the dispersionless flatband segments in the energy spectra are derived. We examine the evolution of the Landau levels when an in-plane lateral electric field is applied, and we determine analytically how the edge states shift withmagnetic field. For wider nanoribbons, the conductance is shown to have a characteristic staircase shape in combined magnetic and electric fields. Some of the stairs in zigzag and skewed armchair nanoribbons originate from edge states that are found in the band gap.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 8
DOI: 10.1103/PHYSREVB.96.125434
|
|
|
“Quantum transport across van der Waals domain walls in bilayer graphene”. Abdullah HM, Van Duppen B, Zarenia M, Bahlouli H, Peeters FM, Journal of physics : condensed matter 29, 425303 (2017). http://doi.org/10.1088/1361-648X/AA81A8
Abstract: Bilayer graphene can exhibit deformations such that the two graphene sheets are locally detached from each other resulting in a structure consisting of domains with different van der Waals inter-layer coupling. Here we investigate how the presence of these domains affects the transport properties of bilayer graphene. We derive analytical expressions for the transmission probability, and the corresponding conductance, across walls separating different inter-layer coupling domains. We find that the transmission can exhibit a valley-dependent layer asymmetry and that the domain walls have a considerable effect on the chiral tunnelling properties of the charge carriers. We show that transport measurements allow one to obtain the strength with which the two layers are coupled. We perform numerical calculations for systems with two domain walls and find that the availability of multiple transport channels in bilayer graphene significantly modifies the conductance dependence on inter-layer potential asymmetry.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.649
Times cited: 15
DOI: 10.1088/1361-648X/AA81A8
|
|
|
“Advanced first-principles theory of superconductivity including both lattice vibrations and spin fluctuations : the case of FeB4”. Bekaert J, Aperis A, Partoens B, Oppeneer PM, Milošević, MV, Physical review B 97, 014503 (2018). http://doi.org/10.1103/PHYSREVB.97.014503
Abstract: <script type='text/javascript'>document.write(unpmarked('We present an advanced method to study spin fluctuations in superconductors quantitatively and entirely from first principles. This method can be generally applied to materials where electron-phonon coupling and spin fluctuations coexist. We employ it here to examine the recently synthesized superconductor iron tetraboride (FeB4) with experimental T-c similar to 2.4 K [H. Gou et al., Phys. Rev. Lett, 111, 157002 (2013)]. We prove that FeB4 is particularly prone to ferromagnetic spin fluctuations due to the presence of iron, resulting in a large Stoner interaction strength, I = 1.5 eV, as calculated from first principles. The other important factor is its Fermi surface that consists of three separate sheets, among which two are nested ellipsoids. The resulting susceptibility has a ferromagnetic peak around q = 0, from which we calculated the repulsive interaction between Cooper pair electrons using the random phase approximation. Subsequently, we combined the electron-phonon interaction calculated from first principles with the spin fluctuation interaction in fully anisotropic Eliashberg theory calculations. We show that the resulting superconducting gap spectrum is conventional, yet very strongly depleted due to coupling to the spin fluctuations. The critical temperature decreases from T-c = 41 K, if they are not taken into account, to T-c = 1.7 K, in good agreement with the experimental value.'));
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 23
DOI: 10.1103/PHYSREVB.97.014503
|
|
|
“Ballistic electron channels including weakly protected topological states in delaminated bilayer graphene”. Lane TLM, Andelkovic M, Wallbank JR, Covaci L, Peeters FM, Fal'ko VI, Physical review B 97, 045301 (2018). http://doi.org/10.1103/PHYSREVB.97.045301
Abstract: <script type='text/javascript'>document.write(unpmarked('We show that delaminations in bilayer graphene (BLG) with electrostatically induced interlayer symmetry can provide one with ballistic channels for electrons with energies inside the electrostatically induced BLG gap. These channels are formed by a combination of valley-polarized evanescent states propagating along the delamination edges (which persist in the presence of a strong magnetic field) and standing waves bouncing between them inside the delaminated region (in a strong magnetic field, these transform into Landau levels in the monolayers). For inverted stackings in BLGs on the left and right of the delamination (AB-2ML-BA or BA-2ML-AB, where 2ML indicates two decoupled monolayers of graphene), the lowest-energy ballistic channels are gapless, have linear dispersion, and appear to be weakly topologically protected. When BLG stackings on both sides of the delamination are the same (AB-2ML-AB or BA-2ML-BA), the lowest-energy ballistic channels are gapped, with a gap epsilon(g) scaling as epsilon(g) alpha W-1 with delamination width and epsilon(g) alpha delta(-1) with the on-layer energy difference in the delaminated part of the structure. Depending on the width, delaminations may also support several \u0022higher-energy\u0022 waveguide modes. Our results are based on both the analytical study of the wave matching of Dirac states and tight-binding model calculations, and we analyze in detail the dependence of the delamination spectrum on the electrostatic conditions in the structure, such as the vertical displacement field.'));
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 11
DOI: 10.1103/PHYSREVB.97.045301
|
|
|
“Helical edge states in silicene and germanene nanorings in perpendicular magnetic field”. Jakovljevic DZ, Grujic MM, Tadic MZ, Peeters FM, Journal of physics : condensed matter 30, 035301 (2018). http://doi.org/10.1088/1361-648X/AA9E67
Abstract: <script type='text/javascript'>document.write(unpmarked('Due to nonzero intrinsic spin-orbit interaction in buckled honeycomb crystal structures, silicene and germanene exhibit interesting topological properties, and are therefore candidates for the realization of the quantum spin Hall effect. We employ the Kane-Mele model to investigate the electron states in hexagonal silicene and germanene nanorings having either zigzag or armchair edges in the presence of a perpendicular magnetic field. We present results for the energy spectra as function of magnetic field, the electron density of the spin-up and spin-down states in the ring plane, and the calculation of the probability current density. The quantum spin Hall phase is found at the edges between the nontrivial topological phase in silicene and germanene and vacuum. We demonstrate that the helical edge states in zigzag silicene and germanene nanorings can be qualitatively well understood by means of classical magnetic moments. However, this is not the case for comparable-sized armchair nanorings, where the eigenfunctions spread throughout the ring. Finally, we note that the energy spectra of silicene and germanene nanorings are similar and that the differences between the two are mainly related to the difference in magnitude of the spin-orbit coupling.'));
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.649
Times cited: 4
DOI: 10.1088/1361-648X/AA9E67
|
|
|
“Magnetic field dependence of the atomic collapse state in graphene”. Moldovan D, Masir MR, Peeters FM, 2D materials 5, 015017 (2018). http://doi.org/10.1088/2053-1583/AA9647
Abstract: <script type='text/javascript'>document.write(unpmarked('Quantum electrodynamics predicts that heavy atoms (Z \u003E Z(c) approximate to 170) will undergo the process of atomic collapse where electrons sink into the positron continuum and a new family of so-called collapsing states emerges. The relativistic electrons in graphene exhibit the same physics but at a much lower critical charge (Z(c) approximate to 1) which has made it possible to confirm this phenomenon experimentally. However, there exist conflicting predictions on the effect of a magnetic field on atomic collapse. These theoretical predictions are based on the continuum Dirac-Weyl equation, which does not have an exact analytical solution for the interplay of a supercritical Coulomb potential and the magnetic field. Approximative solutions have been proposed, but because the two effects compete on similar energy scales, the theoretical treatment varies depending on the regime which is being considered. These limitations are overcome here by starting from a tight-binding approach and computing exact numerical results. By avoiding special limit cases, we found a smooth evolution between the different regimes. We predict that the atomic collapse effect persists even after the magnetic field is activated and that the critical charge remains unchanged. We show that the atomic collapse regime is characterized: (1) by a series of Landau level anticrossings and (2) by the absence of root B scaling of the Landau levels with regard to magnetic field strength.'));
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 6.937
Times cited: 13
DOI: 10.1088/2053-1583/AA9647
|
|
|
“Multicomponent electron-hole superfluidity and the BCS-BEC crossover in double bilayer graphene”. Conti S, Perali A, Peeters FM, Neilson D, Physical review letters 119, 257002 (2017). http://doi.org/10.1103/PHYSREVLETT.119.257002
Abstract: <script type='text/javascript'>document.write(unpmarked('Superfluidity in coupled electron-hole sheets of bilayer graphene is predicted here to be multicomponent because of the conduction and valence bands. We investigate the superfluid crossover properties as functions of the tunable carrier densities and the tunable energy band gap Eg. For small band gaps there is a significant boost in the two superfluid gaps, but the interaction-driven excitations from the valence to the conduction band can weaken the superfluidity, even blocking the system from entering the Bose-Einstein condensate (BEC) regime at low densities. At a given larger density, a band gap E-g similar to 80-120 meV can carry the system into the strong-pairing multiband BCS-BEC crossover regime, the optimal range for realization of high-Tc superfluidity.'));
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 8.462
Times cited: 18
DOI: 10.1103/PHYSREVLETT.119.257002
|
|