Electronic magnetization of a quantum point contact measured by nuclear magnetic resonance

TL;DR

This study demonstrates a novel method to measure electronic magnetization in a quantum point contact using NMR spectroscopy, revealing how magnetization varies with conductance and supporting a no bound state explanation for the 0.7 structure.

Contribution

It introduces a new NMR-based technique to directly measure electronic magnetization in QPCs, providing insights into their spin properties and conductance features.

Findings

NMR signals detected via QPC conductance measurements.

Magnetization peaks at the 0.5 conductance plateau.

Results support a no bound state origin of the 0.7 structure.

Abstract

We report an electronic magnetization measurement of a quantum point contact (QPC) based on nuclear magnetic resonance (NMR) spectroscopy. We find that NMR signals can be detected by measuring the QPC conductance under in-plane magnetic fields. This makes it possible to measure, from Knight shifts of the NMR spectra, the electronic magnetization of a QPC containing only a few electron spins. The magnetization changes smoothly with the QPC potential barrier height and peaks at the conductance plateau of 0.5 $\times$ $2e^2/h$. The observed features are well captured by a model calculation assuming a smooth potential barrier, supporting a no bound state origin of the 0.7 structure.