Unconventional transport in low-density two-dimensional Rashba systems

TL;DR

This paper investigates how impurity scattering influences electrical conductivity in low-density 2D Rashba systems, revealing unconventional density dependence and quantized plateaus that persist in quantum calculations.

Contribution

It introduces a full T-matrix approach to study impurity effects, uncovering new features like quantized conductivity plateaus in the ultra-low-density regime.

Findings

Conductivity shows unconventional density dependence.

Quantized plateaus in conductivity as a function of log electron density.

Plateaus persist in full quantum (Kubo) calculations.

Abstract

Rashba spin-orbit coupling appears in 2D systems lacking inversion symmetry, and causes the spin-splitting of otherwise degenerate energy bands into an upper and lower helicity band. In this paper, we explore how impurity scattering affects transport in the ultra-low-density regime where electrons are confined to the lower helicity band. A previous study has investigated the conductivity in this regime using a treatment in the first Born approximation. In this work, we use the full T-matrix to uncover new features of the conductivity. We first compute the conductivity within a semiclassical Boltzmann framework and show that it exhibits an unconventional density dependence due to the unusual features of the group velocity in the single particle dispersion, as well as quantized plateaus as a function of the logarithm of the electron density. We support this with a calculation using the Kubo formula and find that these plateaus persist in the full quantum theory. We suggest that this quantization may be seen in a pump-probe experiment.