Dynamic nuclear polarization at the edge of a two-dimensional electron gas

TL;DR

This paper investigates how hyperfine interactions and nuclear spin polarization influence electron transport at the edges of a two-dimensional electron gas in GaAs/AlGaAs heterostructures, revealing diode-like behavior and spin effects.

Contribution

It demonstrates the role of nuclear spin polarization in electronic properties at 2DEG edges, highlighting hyperfine interactions' significance in such systems.

Findings

Diode-like nonlinear transport behavior observed.

Nuclear spin polarization significantly affects spin splitting.

Hyperfine interaction influences edge state electronic properties.

Abstract

We have used gated GaAs/AlGaAs heterostructures to explore nonlinear transport between spin-resolved Landau level (LL) edge states over a submicron region of two-dimensional electron gas (2DEG). The current I flowing from one edge state to the other as a function of the voltage V between them shows diode-like behavior---a rapid increase in I above a well-defined threshold V_t under forward bias, and a slower increase in I under reverse bias. In these measurements, a pronounced influence of a current-induced nuclear spin polarization on the spin splitting is observed, and supported by a series of NMR experiments. We conclude that the hyperfine interaction plays an important role in determining the electronic properties at the edge of a 2DEG.