Spin-orbit interaction induced singularity of the charge density relaxation propagator

TL;DR

This paper investigates how combined spin-orbit interactions in a 2D electron system cause singularities in the charge density relaxation propagator, revealing new ways to control carrier relaxation via electric fields.

Contribution

It provides an intuitive explanation for the singularities caused by combined Bychkov-Rashba and Dresselhaus spin-orbit couplings and identifies conditions where regular behavior is restored.

Findings

Singularities occur at specific bosonic momenta related to spin-orbit coupling.

Regular behavior is restored with only one type of spin-orbit interaction.

Electric fields can potentially modulate carrier relaxation properties.

Abstract

The charge density relaxation propagator of a two dimensional electron system, which is the slope of the imaginary part of the polarization function, exhibits singularities for bosonic momenta having the order of the spin-orbit momentum and depending on the momentum orientation. We have provided an intuitive understanding for this non-analytic behavior in terms of the inter chirality subband electronic transitions, induced by the combined action of Bychkov-Rashba (BR) and Dresselhaus (D) spin-orbit coupling. It is shown that the regular behavior of the relaxation propagator is recovered in the presence of only one BR or D spin-orbit field or for spin-orbit interaction with equal BR and D coupling strengths. This creates a new possibility to influence carrier relaxation properties by means of an applied electric field.