Dynamic nuclear polarization at high Landau levels in a quantum point contact

TL;DR

This paper presents a novel method for polarizing and detecting nuclear spins in a quantum point contact at high Landau levels using resistively-detected NMR, effective at low magnetic fields and preserving spin degeneracy.

Contribution

It introduces a new RDNMR technique that works at high Landau levels and low magnetic fields, enabling studies of electronic states near zero magnetic field.

Findings

RDNMR achieved up to the 5th Landau level at fields below 1 T

RDNMR signals preserved when spin degeneracy of the 1D subband remains

Orbital effects minimized compared to electrostatic confinement

Abstract

We demonstrate a way to polarize and detect nuclear spin in a gate-defined quantum point contact operating at high Landau levels. Resistively-detected Nuclear Magnetic Resonance (RDNMR) can be achieved up to the $5$th Landau level and at a magnetic field lower than $1$ T. We are able to retain the RDNMR signals in a condition where the spin degeneracy of the first 1D subband is still preserved. Furthermore, the effects of orbital motion on the first 1D subband can be made smaller than those due to electrostatic confinement. This developed RDNMR technique is a promising means to study electronic states in a quantum point contact near zero magnetic field.