Width dependence of the 0.5 × (2e2/h) conductance plateau in InAs quantum point contacts in presence of lateral spin-orbit coupling

Abstract

The evolution of the 0.5G o (G o = 2e 2 /h) conductance plateau and the accompanying hysteresis loop in a series of asymmetrically biased InAs based quantum point contacts (QPCs) in the presence of lateral spin-orbit coupling (LSOC) is studied using a number of QPCs with varying lithographic channel width but fixed channel length. It is found that the size of the hysteresis loops is larger for QPCs of smaller aspect ratio (QPC channel width/length) and gradually disappears as their aspect ratio increases. The physical mechanisms responsible for a decrease in size of the hysteresis loops for QPCs with increasing aspect ratio are: (1) multimode transport in QPCs with larger channel width leading to spin-flip scattering events due to both remote impurities in the doping layer of the heterostructure and surface roughness and impurity (dangling bond) scattering on the sidewalls of the narrow portion of the QPC, and (2) an increase in carrier density resulting in a screening of the electron-electron interactions in the QPC channel. Both effects lead to a progressive disappearance of the net spin polarization in the QPC channel and an accompanying reduction in the size of the hysteresis loops as the lithographic width of the QPC channel increases.

Suspended semiconductor nanostructures: physics and technology

“…It was suggested that this may be due to the increased role of the e-e interaction in longer QPCs [107]. Further the effect of channel width on the 0.5 conductance plateau was studied in an InAs-based QPC [108]. It was shown experimentally that the 0.5 plateau became more pronounced with decreasing QPC width.…”

Totally Spin-Polarized Currents in an Interferometer with Spin–Orbit Coupling and the Absence of Magnetic Field Effects

“…Magnetic fields, magnetic materials, and the injection of spin-polarized currents [17][18][19][20][21][22][23][24][25][26][27] or time-dependent Hamiltonians [28] have been used to break this symmetry and generate or manipulate spin-polarized currents. To obtain this result in non-magnetic materials, or without applying an external magnetic field, several systems have been proposed, such as point contact [29,30], graphene nanostructures [31], planar systems with SOC and corrugated graphene nanoribbons [32][33][34], or even creating spin-dependent chemical potentials by microwave irradiation [35]. In reference [29], the authors reported a plateau in the conductance of quantum point contact (QPC) devices, which was suggested to be intrinsically related to the spontaneous spin polarization induced by lateral SOC for sufficiently high asymmetry of the lateral confinement.…”