Fluctuation relations for spin currents

TL;DR

This paper extends the fluctuation theorem to spin currents, deriving model-independent relations between transport coefficients and fluctuations, and applies these to phenomena like the spin Seebeck effect.

Contribution

It introduces a general fluctuation relation for spin currents based on microscopic reversibility, applicable without specific microscopic models.

Findings

Derived a family of fluctuation relations for spin currents.

Applied relations to the spin Seebeck effect and spin current rectification.

Relations serve as tests for theoretical approximations in spin transport.

Abstract

The fluctuation theorem establishes general relations between transport coefficients and fluctuations in nonequilibrium systems. Recently there was much interest in quantum fluctuation relations for electric currents. Since charge carriers also carry spin, it is important to extend the fluctuation theorem to spin currents. We use the principle of microscopic reversibility to derive such theorem. As a consequence, we obtain a family of relations between transport coefficients and fluctuations of spin currents. We apply the relations to the spin Seebeck effect and rectification of spin currents. Our relations do not depend on a microscopic model and hence can be used to test the validity of theoretical approximations in spin-transport problems.