Shot Noise Induced by Electron-nuclear Spin-flip Scattering in a Nonequilibrium Quantum Wire

TL;DR

This paper investigates how electron-nuclear spin-flip scattering causes shot noise and reduces electron spin polarization in a nonequilibrium quantum wire, revealing the impact on conductance quantization in the quantum Hall regime.

Contribution

It demonstrates the role of electron-nuclear spin-flip scattering in shot noise generation and spin polarization reduction in a nonequilibrium quantum wire.

Findings

Spin polarization reduces to ~0.7 due to spin-flip scattering.

Shot noise measurements confirm the reduction in spin polarization.

Conductance quantization collapses under nonequilibrium conditions.

Abstract

We study the shot noise (nonequilibrium current fluctuation) associated with dynamic nuclear polarization in a nonequilibrium quantum wire (QW) fabricated in a two-dimensional electron gas. We observe that the spin-polarized conductance quantization of the QW in the integer quantum Hall regime collapses when the QW is voltage biased to be driven to nonequilibrium. By measuring the shot noise, we prove that the spin polarization of electrons in the QW is reduced to $\sim 0.7$ instead of unity as a result of electron-nuclear spin-flip scattering. The result is supported by Knight shift measurements of the QW using resistively detected NMR.