Semiclassical dynamics and transport of the Dirac spin

TL;DR

This paper develops a semiclassical framework for Dirac electrons to understand spin dynamics and transport, revealing geometric gauge effects and explaining phenomena like spin-Hall and spin-Nernst effects.

Contribution

It introduces a wavepacket-based semiclassical theory for Dirac electrons, linking geometric gauge structures to spin-related transport phenomena.

Findings

Wavepacket size equals the Compton wavelength.

Self-rotation of the wavepacket accounts for the spin magnetic moment.

Geometric gauge structure explains spin-orbit coupling and Yafet terms.

Abstract

A semiclassical theory of spin dynamics and transport is formulated using the Dirac electron model. This is done by constructing a wavepacket from the positive-energy electron band, and studying its structure and center of mass motion. The wavepacket has a minimal size equal to the Compton wavelength, and has self-rotation about the average spin angular momentum, which gives rise to the spin magnetic moment. Geometric gauge structure in the center of mass motion provides a natural explanation of the spin-orbit coupling and various Yafet terms. Applications of the spin-Hall and spin-Nernst effects are discussed.