Measuring Spin Accumulations with Current Noise

TL;DR

This paper demonstrates how current noise measurements can directly quantify spin accumulations in mesoscopic conductors, revealing temperature-dependent saturation and sample-specific asymmetries due to spin-orbit interactions.

Contribution

It introduces a novel electric measurement protocol that uses current noise to determine spin accumulations, highlighting effects of temperature and spin-orbit coupling.

Findings

Current noise saturates at a value set by spin accumulation at low temperatures.

Spin-orbit interactions cause sample-dependent asymmetries in current noise.

The method provides a purely electrical way to measure spin accumulations.

Abstract

We investigate the time-dependent fluctuations of the electric current injected from a reservoir with a non-equilibrium spin accumulation into a mesoscopic conductor. We show how the current noise power directly reflects the magnitude of the spin accumulation in two easily noticeable ways. First, as the temperature is lowered, the small-bias noise saturates at a value determined by the spin accumulation. Second, in the presence of spin-orbit interactions in the conductor, the current noise exhibits a sample-dependent mesoscopic asymmetry under reversal of the electric current direction. These features provide for a purely electric protocol for measuring spin accumulations.