A half-step in quantized conductance for low-density electrons in a quantum wire

TL;DR

This paper explores the effects of magnetic fields and spin-orbit interaction on quantum wire conductance, reproducing a half-step feature and predicting new phenomena related to band structure and nonlinear transport.

Contribution

It provides a theoretical analysis of conductance and thermoelectric power in quantum wires considering spin-orbit interaction and magnetic fields, explaining experimental observations and predicting new effects.

Findings

Reproduced the low-temperature half-step in conductance observed experimentally.

Identified a new peak in thermoelectric power related to band structure features.

Predicted side peaks in conductance at high bias and quadratic bias dependence near zero bias.

Abstract

We investigated the effect due to perpendicular magnetic field on quantum wires where spin-orbit interaction (SOI) of electrons is not neglected. Based on the calculated energy dispersion, the nonlinear ballistic conductance ($G$) and electron-diffusion thermoelectric power ($S_d$) are calculated as functions of electron density, temperature and applied bias voltage. A low-temperature half-step feature in $G$, which was observed experimentally by Quay et al. [see Nature Physics {\bf 6}, 336 (2010)], as well as a new peak in $S_d$ are reproduced here in the low density regime. These phenomena are related to the occurrence of the Zeeman splitting and SOI induced saddle point in the band structure, where the channel chemical potential lies within an anticrossing gap between the saddle point of the lower subband and the bottom of the upper subband. Additionally, side peaks in $G$ far away from the zero bias for the nonlinear transport, as well as a quadratic bias-voltage dependence of $G$ near zero voltage, are predicted and discussed.