Diffusive-Ballistic Crossover and the Persistent Spin Helix

TL;DR

This paper develops a semiclassical transport theory that accurately describes the crossover from diffusive to ballistic regimes in systems with SU(2) symmetric spin-orbit coupling, including large spin precession angles.

Contribution

It introduces a comprehensive theory valid across the diffusive-ballistic crossover, extending beyond the small-angle approximation and providing exact density and spin structure factors.

Findings

Exact expressions for structure factors in 2D and 3D systems.

Valid in regimes with large spin precession angles.

Bridges the gap between diffusive and ballistic transport theories.

Abstract

Conventional transport theory focuses on either the diffusive or ballistic regimes and neglects the crossover region between the two. In the presence of spin-orbit coupling, the transport equations are known only in the diffusive regime, where the spin precession angle is small. In this paper, we develop a semiclassical theory of transport valid throughout the diffusive - ballistic crossover of a special SU(2) symmetric spin-orbit coupled system. The theory is also valid in the physically interesting regime where the spin precession angle is large. We obtain exact expressions for the density and spin structure factors in both 2 and 3 dimensional samples with spin-orbit coupling.