اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدHartree simulations of coupled quantum Hall edge states in corner-overgrown heterostructures
197
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
The electronic states in a corner-overgrown bent GaAs/AlGaAs quantum well heterostructure are studied with numerical Hartree simulations. Transmission electron microscope pictures of the junction justify the sharp-corner assumption. In a tilted magnetic field both facets of the bent quantum well are brought to a quantum Hall (QH) state, and the corner hosts an unconventional hybrid system of two coupled counter-propagating quantum Hall edges and an additional one-dimensional accumulation wire. A subsystems model is introduced, whereby the total hybrid dispersion and wavefunctions are explained in terms of the constituent QH edge- and accumulation wire-subsystem dispersions and wavefunctions. At low magnetic fields, orthonormal basis wavefunctions of the hybrid system can be accurately estimated by projecting out the lowest bound state of the accumulation wire from the edge state wavefunctions. At high magnetic fields, the coupling between the three subsystems increases as a function of the applied magnetic field, in contrast to coplanar barrier-junctions of QH systems, leading to large anticrossing gaps between the subsystem dispersions. These results are discussed in terms of previously reported experimental data on bent quantum Hall systems.
قيم البحث
اقرأ أيضاً
We report conductance measurements in quantum wires made of aluminum arsenide, a heavy-mass, multi-valley one-dimensional (1D) system. Zero-bias conductance steps are observed as the electron density in the wire is lowered, with additional steps obse
rvable upon applying a finite dc bias. We attribute these steps to depopulation of successive 1D subbands. The quantum conductance is substantially reduced with respect to the anticipated value for a spin- and valley-degenerate 1D system. This reduction is consistent with disorder-induced, intra-wire backscattering which suppresses the transmission of 1D modes. Calculations are presented to demonstrate the role of strain in the 1D states of this cleaved-edge structure.
Topologically protected gapless edge states are phases of quantum matter which behave as massless Dirac fermions, immunizing against disorders and continuous perturbations. Recently, a new class of topological insulators (TIs) with topological corner
states have been theoretically predicted in electric systems, and experimentally realized in two-dimensional (2D) mechanical and electromagnetic systems, electrical circuits, optical and sonic crystals, and elastic phononic plates. Here, we demonstrate a pseudospin-valley-coupled phononic TI, which simultaneously exhibits gapped edge states and topological corner states. Pseudospin-orbit coupling edge states and valley-polarized edge state are respectively induced by the lattice deformation and the symmetry breaking. When both of them coexist, these topological edge states will be greatly gapped and the topological corner state emerges. Under direct field measurements, the robust edge propagation behaving as an elastic waveguide and the topological corner mode working as a robust localized resonance are experimentally confirmed. The pseudospin-valley coupling in our phononic TIs can be well-controlled which provides a reconfigurable platform for the multiple edge and corner states, and exhibits well applications in the topological elastic energy recovery and the highly sensitive sensing.
We present a microscopic theory of the chiral one-dimensional electron gas system localized on the sidewalls of magnetically-doped Bi$_2$Se$_3$-family topological insulator nanoribbons in the quantum anomalous Hall effect (QAHE) regime. Our theory is
based on a simple continuum model of sidewall states whose parameters are extracted from detailed ribbon and film geometry tight-binding model calculations. In contrast to the familiar case of the quantum Hall effect in semiconductor quantum wells, the number of microscopic chiral channels depends simply and systematically on the ribbon thickness and on the position of the Fermi level within the surface state gap. We use our theory to interpret recent transport experiments that exhibit non-zero longitudinal resistance in samples with accurately quantized Hall conductances.
We operate an on-demand source of single electrons in high perpendicular magnetic fields up to 30T, corresponding to a filling factor below 1/3. The device extracts and emits single charges at a tunable energy from and to a two-dimensional electron g
as, brought into well defined integer and fractional quantum Hall (QH) states. It can therefore be used for sensitive electrical transport studies, e.g. of excitations and relaxation processes in QH edge states.
We study the low energy edge states of bilayer graphene in a strong perpendicular magnetic field. Several possible simple boundaries geometries related to zigzag edges are considered. Tight-binding calculations reveal three types of edge state behavi
ors: weakly, strongly, and non-dispersive edge states. These three behaviors may all be understood within a continuum model, and related by non-linear transformations to the spectra of quantum Hall edge--states in a conventional two-dimensional electron system. In all cases, the edge states closest to zero energy include a hole-like edge state of one valley and a particle-like state of the other on the same edge, which may or may not cross depending on the boundary condition. Edge states with the same spin generically have anticrossings that complicate the spectra, but which may be understood within degenerate perturbation theory. The results demonstrate that the number of edge states crossing the Fermi level in clean, undoped bilayer graphene depends BOTH on boundary conditions and the energies of the bulk states.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
