Nuclear Polarization in Quantum Point Contacts in an In-Plane Magnetic Field

TL;DR

This paper demonstrates nuclear spin polarization in GaAs quantum point contacts under in-plane magnetic fields, revealing hysteresis in transport properties and providing insights into spin-sensitive conductance features without edge states.

Contribution

It introduces nuclear polarization effects in QPCs with in-plane magnetic fields, expanding understanding beyond out-of-plane field scenarios.

Findings

Nuclear polarization causes hysteresis in QPC conductance.

Relaxation timescales of nuclear polarization are around 100 seconds.

Nuclear polarization influences spin-sensitive transport features.

Abstract

Nuclear spin polarization is typically generated in GaAs quantum point contacts (QPCs) when an out-of-plane magnetic field gives rise to spin-polarized quantum Hall edge states, and a voltage bias drives transitions between the edge states via electron-nuclear flip-flop scattering. Here, we report a similar effect for QPCs in an in-plane magnetic field, where currents are spin polarized but edge states are not formed. The nuclear polarization gives rise to hysteresis in the d.c. transport characteristics, with relaxation timescales around 100 seconds. The dependence of anomalous QPC conductance features on nuclear polarization provides a useful test of their spin-sensitivity.