“Adsorption of H2O, NH3, CO, NO2, and NO on graphene: a first-principles study”. Leenaerts O, Partoens B, Peeters FM, Physical review : B : condensed matter and materials physics 77, 125416 (2008). http://doi.org/10.1103/PhysRevB.77.125416
Abstract: Motivated by the recent realization of graphene sensors to detect individual gas molecules, we investigate the adsorption of H2O, NH3, CO, NO2, and NO on a graphene substrate using first-principles calculations. The optimal adsorption position and orientation of these molecules on the graphene surface is determined and the adsorption energies are calculated. Molecular doping, i.e., charge transfer between the molecules and the graphene surface, is discussed in light of the density of states and the molecular orbitals of the adsorbates. The efficiency of doping of the different molecules is determined and the influence of their magnetic moment is discussed.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 1392
DOI: 10.1103/PhysRevB.77.125416
|
“Phonon softening and direct to indirect band gap crossover in strained single-layer MoSe2”. Horzum S, Sahin H, Cahangirov S, Cudazzo P, Rubio A, Serin T, Peeters FM, Physical review : B : condensed matter and materials physics 87, 125415 (2013). http://doi.org/10.1103/PhysRevB.87.125415
Abstract: Motivated by recent experimental observations of Tongay et al. [Nano Lett. 12, 5576 (2012)] we show how the electronic properties and Raman characteristics of single layer MoSe2 are affected by elastic biaxial strain. We found that with increasing strain: (1) the E' and E '' Raman peaks (E-2g and E-1g in bulk) exhibit significant redshifts (up to similar to 30 cm(-1)), (2) the position of the A'(1) peak remains at similar to 180 cm(-1) (A(1g) in bulk) and does not change considerably with further strain, (3) the dispersion of low energy flexural phonons crosses over from quadratic to linear, and (4) the electronic band structure undergoes a direct to indirect band gap crossover under similar to 3% biaxial tensile strain. Thus the application of strain appears to be a promising approach for a rapid and reversible tuning of the electronic, vibrational, and optical properties of single layer MoSe2 and similar MX2 dichalcogenides. DOI:10.1103/PhysRevB.87.125415
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 171
DOI: 10.1103/PhysRevB.87.125415
|
“Piezoelectricity in two-dimensional materials : comparative study between lattice dynamics and ab initio calculations”. Michel KH, Çakir D, Sevik C, Peeters FM, Physical review B 95, 125415 (2017). http://doi.org/10.1103/PHYSREVB.95.125415
Abstract: The elastic constant C-11 and piezoelectric stress constant e(1),(11) of two-dimensional (2D) dielectric materials comprising h-BN, 2H-MoS2, and other transition-metal dichalcogenides and dioxides are calculated using lattice dynamical theory. The results are compared with corresponding quantities obtained with ab initio calculations. We identify the difference between clamped-ion and relaxed-ion contributions with the dependence on inner strains which are due to the relative displacements of the ions in the unit cell. Lattice dynamics allows us to express the inner-strain contributions in terms of microscopic quantities such as effective ionic charges and optoacoustical couplings, which allows us to clarify differences in the piezoelectric behavior between h-BN and MoS2. Trends in the different microscopic quantities as functions of atomic composition are discussed.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 29
DOI: 10.1103/PHYSREVB.95.125415
|
“Peculiar half-metallic state in zigzag nanoribbons of MoS2 : spin filtering”. Khoeini F, Shakouri, Peeters FM, Physical review B 94, 125412 (2016). http://doi.org/10.1103/PHYSREVB.94.125412
Abstract: Layered structures of molybdenum disulfide (MoS2) belong to a new class of two-dimensional (2D) semiconductor materials in which monolayers exhibit a direct band gap in their electronic spectrum. This band gap has recently been shown to vanish due to the presence of metallic edge modes when MoS2 monolayers are terminated by zigzag edges on both sides. Here, we demonstrate that a zigzag nanoribbon of MoS2, when exposed to an external exchange field in combination with a transverse electric field, has the potential to exhibit a peculiar half-metallic nature and thereby allows electrons of only one spin direction to move. The peculiarity of such spin-selective conductors originates from a spin switch near the gap-closing region, so the allowed spin orientation can be controlled by means of an external gate voltage. It is shown that the induced half-metallic phase is resistant to random fluctuations of the exchange field as well as the presence of edge vacancies.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 38
DOI: 10.1103/PHYSREVB.94.125412
|
“Bound states and lifetime of an electron on a bulk helium surface”. Degani MH, Farias GA, Peeters FM, Physical review : B : condensed matter and materials physics 72, 125408 (2005). http://doi.org/10.1103/PhysRevB.72.125408
Abstract: We propose an effective potential for an excess electron near the helium liquid-vapor interface that takes into account the diffuseness of the liquid-vapor interface and the classical image potential. The splitting of the first two excited states of the excess electron bound to the helium liquid-vapor interface as a function of an external constant electric field applied perpendicular to the interface is in excellent agreement with recent experiments. The effect of a parallel magnetic field on the energy levels are calculated. Single-electron tunneling of the electron out of its surface state is studied as a function of the electric field applied to the system. We found that the tunneling time has a linear dependence on the electric field.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 11
DOI: 10.1103/PhysRevB.72.125408
|
“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
|
“Bilayer SnS2 : tunable stacking sequence by charging and loading pressure”. Bacaksiz C, Cahangirov S, Rubio A, Senger RT, Peeters FM, Sahin H, Physical review B 93, 125403 (2016). http://doi.org/10.1103/PhysRevB.93.125403
Abstract: Employing density functional theory-based methods, we investigate monolayer and bilayer structures of hexagonal SnS2, which is a recently synthesized monolayer metal dichalcogenide. Comparison of the 1H and 1T phases of monolayer SnS2 confirms the ground state to be the 1T phase. In its bilayer structure we examine different stacking configurations of the two layers. It is found that the interlayer coupling in bilayer SnS2 is weaker than that of typical transition-metal dichalcogenides so that alternative stacking orders have similar structural parameters and they are separated with low energy barriers. A possible signature of the stacking order in the SnS2 bilayer has been sought in the calculated absorbance and reflectivity spectra. We also study the effects of the external electric field, charging, and loading pressure on the characteristic properties of bilayer SnS2. It is found that (i) the electric field increases the coupling between the layers at its preferred stacking order, so the barrier height increases, (ii) the bang gap value can be tuned by the external E field and under sufficient E field, the bilayer SnS2 can become a semimetal, (iii) the most favorable stacking order can be switched by charging, and (iv) a loading pressure exceeding 3 GPa changes the stacking order. The E-field tunable band gap and easily tunable stacking sequence of SnS2 layers make this 2D crystal structure a good candidate for field effect transistor and nanoscale lubricant applications.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 38
DOI: 10.1103/PhysRevB.93.125403
|
“Spin-dependent tunneling in diluted magnetic semiconductor trilayer structures”. Krstajic P, Peeters FM, Physical review : B : condensed matter and materials physics 72, 125350 (2005). http://doi.org/10.1103/PhysRevB.72.125350
Abstract: Tunneling of holes through a trilayer structure made of two diluted magnetic semiconductors, (Ga,Mn)As, separated by a thin layer of nonmagnetic AlAs is investigated. The problem is treated within the 6x6 Luttinger-Kohn model for valence bands with the split-off band included. The influence of the spin-orbit coupling is pronounced as the spin-splitting Delta(ex) is comparable with the split-off Delta(SO) splitting. It is assumed that direct tunneling is the dominant mechanism due to the high quality of the tunnel junctions. Our theoretical results predict the correct order of magnitude for the tunneling magnetoresistance ratio, but various other effects, such as scattering on impurities and defects, should be included in order to realize a quantitative agreement with experiment.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 8
DOI: 10.1103/PhysRevB.72.125350
|
“Anisotropic quantum dots: Correspondence between quantum and classical Wigner molecules, parity symmetry, and broken-symmetry states”. Szafran B, Peeters FM, Bednarek S, Adamowski J, Physical review : B : condensed matter and materials physics 69, 125344 (2004). http://doi.org/10.1103/PhysRevB.69.125344
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 40
DOI: 10.1103/PhysRevB.69.125344
|
“Intersublevel magnetoabsorption in the valence band of p-type InAs/GaAs and Ge/Si self-assembled quantum dots”. Tadić, M, Peeters FM, Physical review : B : condensed matter and materials physics 71, 125342 (2005). http://doi.org/10.1103/PhysRevB.71.125342
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 7
DOI: 10.1103/PhysRevB.71.125342
|
“Wave packet dynamics in semiconductor quantum rings of finite width”. Chaves A, Farias GA, Peeters FM, Szafran B, Physical review : B : solid state 80, 125331 (2009). http://doi.org/10.1103/PhysRevB.80.125331
Abstract: The time evolution of a wave packet injected into a semiconductor quantum ring is investigated in order to obtain the transmission and reflection probabilities. Within the effective-mass approximation, the time-dependent Schrödinger equation is solved for a system with nonzero width of the ring and leads and finite potential-barrier heights, where we include smooth lead-ring connections. In the absence of a magnetic field, an analysis of the projection of the wave function over the different subband states shows that when the injected wave packet is within a single subband, the junction can scatter this wave packet into different subbands but remarkably at the second junction the wave packet is scattered back into the subband state of the incoming wave packet. If a magnetic field is applied perpendicularly to the ring plane, transmission and reflection probabilities exhibit Aharonov-Bohm (AB) oscillations and the outgoing electrons may end up in different subband states from those of the incoming electrons. Localized impurities, placed in the ring arms, influence the AB oscillation period and amplitude. For a single impurity or potential barrier of sufficiently strong strength, the period of the AB oscillations is halved while for two impurities localized in diametrically opposite points of the ring, the original AB period is recovered. A theoretical investigation of the confined states and time evolution of wave packets in T wires is also made, where a comparison between this system and the lead-ring junction is drawn.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 40
DOI: 10.1103/PhysRevB.80.125331
|
“Stability of spintronic devices based on quantum ring networks”. Földi P, Kálmán O, Peeters FM, Physical review : B : solid state 80, 125324 (2009). http://doi.org/10.1103/PhysRevB.80.125324
Abstract: Transport properties in mesoscopic networks are investigated, where the strength of the (Rashba-type) spin-orbit coupling is tuned with external gate voltages. We analyze in detail to what extent the ideal behavior and functionality of some promising network-based devices are modified by random (spin-dependent) scattering events and by thermal fluctuations. It is found that although the functionality of these devices is obviously based on the quantum coherence of the transmitted electrons, there is a certain stability: moderate level of errors can be tolerated. For mesoscopic networks made of typical semiconductor materials, we found that when the energy distribution of the input carriers is narrow enough, the devices can operate close to their ideal limits even at relatively high temperature. As an example, we present results for two different networks: one that realizes a Stern-Gerlach device and another that simulates a spin quantum walker. Finally we propose a simple network that can act as a narrow band energy filter even in the presence of random scatterers.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 41
DOI: 10.1103/PhysRevB.80.125324
|
“Phonon-induced pure dephasing in exciton-biexciton quantum dot systems driven by ultrafast laser pulse sequences”. Axt VM, Kuhn T, Vagov A, Peeters FM, Physical review : B : condensed matter and materials physics 72, 125309 (2005). http://doi.org/10.1103/PhysRevB.72.125309
Abstract: A semiconductor quantum dot model accounting for single exciton as well as biexciton states coupled to phonons and laser light is investigated in the limit of strong electronic confinement. For an arbitrary sequence of excitations with ultrafast pulses analytical solutions are obtained for all density-matrix elements. The results are nonperturbative with respect to both the carrier-phonon and the carrier-light coupling. Numerical results for a single pulse excitation are presented illustrating spectral features of our solution as well as pulse area and temperature dependences.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 48
DOI: 10.1103/PhysRevB.72.125309
|
“Excitonic Aharonov-Bohm effect : unstrained versus strained type-I semiconductor nanorings”. Tadić, M, Čukarić, N, Arsoski V, Peeters FM, Physical review : B : condensed matter and materials physics 84, 125307 (2011). http://doi.org/10.1103/PhysRevB.84.125307
Abstract: We study how mechanical strain affects the magnetic field dependence of the exciton states in type-I semiconductor nanorings. Strain spatially separates the electron and hole in (In,Ga)As/GaAs nanorings which is beneficial for the occurrence of the excitonic Aharonov-Bohm (AB) effect. In narrow strained (In,Ga)As/GaAs nanorings the AB oscillations in the exciton ground-state energy are due to anticrossings with the first excited state. No such AB oscillations are found in unstrained GaAs/(Al,Ga)As nanorings irrespective of the ring width. Our results are obtained within an exact numerical diagonalization scheme and are shown to be accurately described by a two-level model with off-diagonal coupling t. The later transfer integral expresses the Coulomb coupling between states of electron-hole pairs. We also found that the oscillator strength for exciton recombination in (In,Ga)As/GaAs nanorings exhibits AB oscillations, which are superimposed on a linear increase with magnetic field. Our results agree qualitatively with recent experiments on the excitonic Aharonov-Bohm effect in type-I (In,Ga)As/GaAs nanorings.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 13
DOI: 10.1103/PhysRevB.84.125307
|
“Magnetoconductance of rectangular arrays of quantum rings”. Kálmán O, Földi P, Benedict MG, Peeters FM, Physical review : B : condensed matter and materials physics 78, 125306 (2008). http://doi.org/10.1103/PhysRevB.78.125306
Abstract: Electron transport through multiterminal rectangular arrays of quantum rings is studied in the presence of Rashba-type spin-orbit interaction (SOI) and of a perpendicular magnetic field. Using the analytic expressions for the transmission and reflection coefficients for single rings we obtain the conductance through such arrays as a function of the SOI strength, of the magnetic flux, and of the wave vector k of the incident electron. Due to destructive or constructive spin interferences caused by the SOI, the array can be totally opaque for certain ranges of k, while there are parameter values where it is completely transparent. Spin resolved transmission probabilities show nontrivial spin transformations at the outputs of the arrays. When pointlike random scattering centers are placed between the rings, the Aharonov-Bohm peaks split, and an oscillatory behavior of the conductance emerges as a function of the SOI strength.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 31
DOI: 10.1103/PhysRevB.78.125306
|
“Decoupled DFT-1/2 method for defect excitation energies”. Claes J, Partoens B, Lamoen D, Physical Review B 108, 125306 (2023). http://doi.org/10.1103/PhysRevB.108.125306
Abstract: The DFT-1/2 method is a band-gap correction with GW precision at a density functional theory (DFT) computational cost. The method was also extended to correct the gap between defect levels, allowing for the calculation of optical transitions. However, this method fails when the atomic character of the occupied and unoccupied defect levels is similar as we illustrate by two examples, the tetrahedral hydrogen interstitial and the negatively charged vacancy in diamond. We solve this problem by decoupling the effect of the occupied and unoccupied defect levels and call this the decoupled DFT-1/2 method for defects.
Keywords: A1 Journal Article; Condensed Matter Theory (CMT) ;
Impact Factor: 3.7
DOI: 10.1103/PhysRevB.108.125306
|
“Ground state and vortex structure of the N=5 and N=6 electron quantum dot”. Tavernier MB, Anisimovas E, Peeters FM, Physical review : B : condensed matter and materials physics 74, 125305 (2006). http://doi.org/10.1103/PhysRevB.74.125305
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 23
DOI: 10.1103/PhysRevB.74.125305
|
“Optoelectronic properties of graphene in the presence of optical phonon scattering”. Xu W, Dong HM, Li LL, Yao JQ, Vasilopoulos P, Peeters FM, Physical review : B : condensed matter and materials physics 82, 125304 (2010). http://doi.org/10.1103/PhysRevB.82.125304
Abstract: We study in detail the optoelectronic properties of graphene. Considering the electron interactions with photons and phonons, we employ the mass- and energy-balance equations to self-consistently evaluate the photoinduced carrier densities, the optical conductance, and the transmission coefficient in the presence of a linearly polarized radiation field. We demonstrate that the photoinduced carrier densities increase around the electron-photon-phonon resonant transition. They depend strongly on the radiation intensity and frequency, temperature, and dark carrier density. For short-wavelength radiation (L<3 μm), we obtain the universal optical conductance σ0=e2/(4ℏ). Importantly, there exists an optical-absorption window in the radiation wavelength range 4100 μm, which is induced by different transition energies required for interband and intraband optical absorption. The position and width of this window depend sensitively on the temperature and the carrier density of the system. These theoretical results are in line with recent experimental findings and indicate that graphene exhibits important features not only in the visible regime but also in the midinfrared bandwidth.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 28
DOI: 10.1103/PhysRevB.82.125304
|
“Confined electron states in two-dimensional HgTe in magnetic field : quantum dot versus quantum ring behavior”. Topalovic DB, Arsoski VV, Tadic MZ, Peeters FM, Physical review B 100, 125304 (2019). http://doi.org/10.1103/PHYSREVB.100.125304
Abstract: We investigate the electron states and optical absorption in square- and hexagonal-shaped two-dimensional (2D) HgTe quantum dots and quantum rings in the presence of a perpendicular magnetic field. The electronic structure is modeled by means of the sp(3)d(5)s* tight-binding method within the nearest-neighbor approximation. Both bulklike and edge states appear in the energy spectrum. The bulklike states in quantum rings exhibit Aharonov-Bohm oscillations in magnetic field, whereas no such oscillations are found in quantum dots, which is ascribed to the different topology of the two systems. When magnetic field varies, all the edge states in square quantum dots appear as quasibands composed of almost fully flat levels, whereas some edge states in quantum rings are found to oscillate with magnetic field. However, the edge states in hexagonal quantum dots are localized like in rings. The absorption spectra of all the structures consist of numerous absorption lines, which substantially overlap even for small line broadening. The absorption lines in the infrared are found to originate from transitions between edge states. It is shown that the magnetic field can be used to efficiently tune the optical absorption of HgTe 2D quantum dot and quantum ring systems.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 4
DOI: 10.1103/PHYSREVB.100.125304
|
“Beating of oscillations in transport coefficients of a one-dimensionally periodically modulatedtwo-dimensional electron gas in the presence of spin-orbit interaction”. Wang XF, Peeters FM, Physical review : B : condensed matter and materials physics 71, 125301 (2005). http://doi.org/10.1103/PhysRevB.71.125301
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 35
DOI: 10.1103/PhysRevB.71.125301
|
“Voltage-controlled superconducting magnetic memory”. Kenawy A, Magnus W, Milošević, MV, Sorée B, AIP advances
T2 –, 64th Annual Conference on Magnetism and Magnetic Materials (MMM), NOV 04-08, 2019, Las Vegas, NV 9, 125223 (2019). http://doi.org/10.1063/1.5129135
Abstract: Over the past few decades, superconducting circuits have been used to realize various novel electronic devices such as quantum bits, SQUIDs, parametric amplifiers, etc. One domain, however, where superconducting circuits fall short is information storage. Superconducting memories are based on the quantization of magnetic flux in superconducting loops. Standard implementations store information as magnetic flux quanta in a superconducting loop interrupted by two Josephson junctions (i.e., a SQUID). However, due to the large inductance required, the size of the SQUID loop cannot be scaled below several micrometers, resulting in low-density memory chips. Here, we propose a scalable memory consisting of a voltage-biased superconducting ring threaded by a half-quantum flux bias. By numerically solving the time-dependent Ginzburg-Landau equations, we show that applying a time-dependent bias voltage in the microwave range constitutes a writing mechanism to change the number of stored flux quanta within the ring. Since the proposed device does not require a large loop inductance, it can be scaled down, enabling a high-density memory technology. (C) 2019 Author(s).
Keywords: A1 Journal article; Engineering sciences. Technology; Condensed Matter Theory (CMT)
DOI: 10.1063/1.5129135
|
“Excitons in coupled InAs/InP self-assembled quantum wires”. Sidor Y, Partoens B, Peeters FM, Ben T, Ponce A, Sales DL, Molina SI, Fuster D, González L, González Y, Physical review : B : condensed matter and materials physics 75, 125120 (2007). http://doi.org/10.1103/PhysRevB.75.125120
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 24
DOI: 10.1103/PhysRevB.75.125120
|
“In-phase motion of Josephson vortices in stacked SNS Josephson junctions : effect of ordered pinning”. Berdiyorov GR, Savel'ev SE, Kusmartsev FV, Peeters FM, Superconductor science and technology 26, 125010 (2013). http://doi.org/10.1088/0953-2048/26/12/125010
Abstract: The dynamics of Josephson vortices (fluxons) in artificial stacks of superconducting-normal-superconducting Josephson junctions is investigated using the anisotropic time-dependent Ginzburg-Landau theory in the presence of a square/rectangular array of pinning centers (holes). For small values of the applied drive, fluxons in different junctions move out of phase, forming a periodic triangular lattice. A rectangular lattice of moving fluxons is observed at larger currents, which is in agreement with previous theoretical predictions (Koshelev and Aranson 2000 Phys. Rev. Lett. 85 3938). This 'superradiant' flux-flow state is found to be stable in a wide region of applied current. The stability range of this ordered state is considerably larger than the one obtained for the pinning-free sample. Clear commensurability features are observed in the current-voltage characteristics of the system with pronounced peaks in the critical current at (fractional) matching fields. The effect of density and strength of the pinning centers on the stability of the rectangular fluxon lattice is discussed. Predicted synchronized motion of fluxons in the presence of ordered pinning can be detected experimentally using the rf response of the system, where enhancement of the Shapiro-like steps is expected due to the synchronization.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.878
Times cited: 5
DOI: 10.1088/0953-2048/26/12/125010
|
“Adaptively time stepping the stochastic Landau-Lifshitz-Gilbert equation at nonzero temperature: Implementation and validation in MuMax3”. Leliaert J, Mulkers J, De Clercq J, Coene A, Dvornik M, Van Waeyenberge B, AIP advances 7, 125010 (2017). http://doi.org/10.1063/1.5003957
Abstract: Thermal fluctuations play an increasingly important role in micromagnetic research relevant for various biomedical and other technological applications. Until now, it was deemed necessary to use a time stepping algorithm with a fixed time step in order to perform micromagnetic simulations at nonzero temperatures. However, Berkov and Gorn have shown in [D. Berkov and N. Gorn, J. Phys.: Condens. Matter,14, L281, 2002] that the drift term which generally appears when solving stochastic differential equations can only influence the length of the magnetization. This quantity is however fixed in the case of the stochastic Landau-Lifshitz-Gilbert equation. In this paper, we exploit this fact to straightforwardly extend existing high order solvers with an adaptive time stepping algorithm. We implemented the presented methods in the freely available GPU-accelerated micromagnetic software package MuMax3 and used it to extensively validate the presented methods. Next to the advantage of having control over the error tolerance, we report a twenty fold speedup without a loss of accuracy, when using the presented methods as compared to the hereto best practice of using Heun’s solver with a small fixed time step.
Keywords: A1 Journal article; Engineering sciences. Technology; Condensed Matter Theory (CMT)
Impact Factor: 1.568
Times cited: 13
DOI: 10.1063/1.5003957
|
“Electronically tunable quantum phase slips in voltage-biased superconducting rings as a base for phase-slip flux qubits”. Kenawy A, Magnus W, Milošević, MV, Sorée B, Superconductor Science &, Technology 33, 125002 (2020). http://doi.org/10.1088/1361-6668/ABB8EB
Abstract: Quantum phase slips represent a coherent mechanism to couple flux states of a superconducting loop. Since their first direct observation, there have been substantial developments in building charge-insensitive quantum phase-slip circuits. At the heart of these devices is a weak link, often a nanowire, interrupting a superconducting loop. Owing to the very small cross-sectional area of such a nanowire, quantum phase slip rates in the gigahertz range can be achieved. Instead, here we present the use of a bias voltage across a superconducting loop to electrostatically induce a weak link, thereby amplifying the rate of quantum phase slips without physically interrupting the loop. Our simulations reveal that the bias voltage modulates the free energy barrier between subsequent flux states in a very controllable fashion, providing a route towards a phase-slip flux qubit with a broadly tunable transition frequency.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.6
Times cited: 4
DOI: 10.1088/1361-6668/ABB8EB
|
“Generalized phonon-assisted Zener tunneling in indirect semiconductors with non-uniform electric fields : a rigorous approach”. Vandenberghe W, Sorée B, Magnus W, Fischetti MV, Journal of applied physics 109, 124503 (2011). http://doi.org/10.1063/1.3595672
Abstract: A general framework to calculate the Zener current in an indirect semiconductor with an externally applied potential is provided. Assuming a parabolic valence and conduction band dispersion, the semiconductor is in equilibrium in the presence of the external field as long as the electron-phonon interaction is absent. The linear response to the electron-phonon interaction results in a non-equilibrium system. The Zener tunneling current is calculated from the number of electrons making the transition from valence to conduction band per unit time. A convenient expression based on the single particle spectral functions is provided, enabling the evaluation of the Zener tunneling current under any three-dimensional potential profile. For a one-dimensional potential profile an analytical expression is obtained for the current in a bulk semiconductor, a semiconductor under uniform field, and a semiconductor under a non-uniform field using the WKB (Wentzel-Kramers-Brillouin) approximation. The obtained results agree with the Kane result in the low field limit. A numerical example for abrupt p-n diodes with different doping concentrations is given, from which it can be seen that the uniform field model is a better approximation than the WKB model, but a direct numerical treatment is required for low bias conditions.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.068
Times cited: 41
DOI: 10.1063/1.3595672
|
“Doping effect on the adsorption of NH3 molecule onto graphene quantum dot : from the physisorption to the chemisorption”. Seyed-Talebi SM, Beheshtian J, Neek-Amal M, Journal of applied physics 114, 124307 (2013). http://doi.org/10.1063/1.4822165
Abstract: The adsorption of ammonia molecule onto a graphene hexagonal flake, aluminum (Al) and boron (B) doped graphene flakes (graphene quantum dots, GQDs) are investigated using density functional theory. We found that NH3 molecule is absorbed to the hollow site through the physisorption mechanism without altering the electronic properties of GQD. However, the adsorption energy of NH3 molecule onto the Al- and B-doped GQDs increases with respect GQD resulting chemisorption. The adsorption of NH3 onto the Al-doped and B-doped GQDs makes graphene locally buckled, i.e., B-doped and Al-doped GQDs are not planar. The adsorption mechanism onto a GQD is different than that of graphene. This study reveals important features of the edge passivation and doping effects of the adsorption mechanism of external molecules onto the graphene quantum dots. (C) 2013 AIP Publishing LLC.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.068
Times cited: 10
DOI: 10.1063/1.4822165
|
“Modeling surface roughness scattering in metallic nanowires”. Moors K, Sorée B, Magnus W, Journal of applied physics 118, 124307 (2015). http://doi.org/10.1063/1.4931573
Abstract: Ando's model provides a rigorous quantum-mechanical framework for electron-surface roughness scattering, based on the detailed roughness structure. We apply this method to metallic nanowires and improve the model introducing surface roughness distribution functions on a finite domain with analytical expressions for the average surface roughness matrix elements. This approach is valid for any roughness size and extends beyond the commonly used Prange-Nee approximation. The resistivity scaling is obtained from the self-consistent relaxation time solution of the Boltzmann transport equation and is compared to Prange-Nee's approach and other known methods. The results show that a substantial drop in resistivity can be obtained for certain diameters by achieving a large momentum gap between Fermi level states with positive and negative momentum in the transport direction. (C) 2015 AIP Publishing LLC.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.068
Times cited: 11
DOI: 10.1063/1.4931573
|
“Tunable magnetic focusing using Andreev scattering in superconductor-graphene hybrid devices”. Chaves A, Moura VN, Linard FJA, Covaci L, Milošević, MV, Journal Of Applied Physics 128, 124303 (2020). http://doi.org/10.1063/5.0020392
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.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Condensed Matter Theory (CMT)
Impact Factor: 3.2
Times cited: 1
DOI: 10.1063/5.0020392
|
“The Cooper problem in nanoscale : enhancement of the coupling due to confinement”. Croitoru MD, Vagov A, Shanenko AA, Axt VM, Superconductor science and technology 25, 124001 (2012). http://doi.org/10.1088/0953-2048/25/12/124001
Abstract: In 1956 Cooper demonstrated (1956 Phys. Rev. 104 1189) that, no matter how weak the attraction is, two electrons in three-dimensional (3D) space just above the Fermi sea could be bound. In this work we investigate the influence of confinement on the binding energy of a Cooper pair. We show that confinement-induced modification of the Fermi sea results in a significant increase of the binding energy, when the bottom of an energy subband is very close to the Fermi surface.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.878
Times cited: 9
DOI: 10.1088/0953-2048/25/12/124001
|