Universal Features of Spin Transport and Breaking of Unitary Symmetries

TL;DR

This paper reveals universal behaviors in spin transport related to symmetry breaking in quantum systems, showing that spin currents can distinguish between different symmetry regimes, especially in single-channel scenarios.

Contribution

It demonstrates that spin transport can differentiate systems with or without time-reversal symmetry, highlighting new universal features in quantum coherence.

Findings

Spin transport is insensitive to time-reversal symmetry breaking in high conductance regimes.

In single-channel systems, spin currents vanish with time-reversal symmetry but appear when it is broken.

Universal behavior of spin transport is characterized across different symmetry classes.

Abstract

When time-reversal symmetry is broken, quantum coherent systems with and without spin rotational symmetry exhibit the same universal behavior in their electric transport properties. We show that spin transport discriminates between these two cases. In systems with large charge conductance, spin transport is essentially insensitive to the breaking of time-reversal symmetry. However, in the opposite limit of a single exit channel, spin currents vanish identically in the presence of time-reversal symmetry, but are turned on by breaking it with an orbital magnetic field.