Persistence of the 0.7 anomaly of quantum point contacts in high magnetic fields

TL;DR

This study investigates the 0.7 anomaly in quantum point contacts, showing that its energy splitting persists under high magnetic fields and is mainly due to a field-independent exchange interaction, despite sample variations.

Contribution

It provides experimental evidence that the 0.7 anomaly's splitting is dominated by exchange interactions, persisting in high magnetic fields and correlating with zero-field splitting.

Findings

The 0.7 anomaly's energy splitting persists in high magnetic fields.

Exchange contribution to splitting shows sample-to-sample fluctuations.

The splitting correlates with the zero-field 0.7 anomaly, indicating exchange dominance.

Abstract

The spin degeneracy of the lowest subband that carries one-dimensional electron transport in quantum point contacts appears to be spontaneously lifted in zero magnetic field due to a phenomenon that is known as the 0.7 anomaly. We measured this energy splitting, and studied how it evolves into a splitting that is the sum of the Zeeman effect and a field-independent exchange contribution when applying a magnetic field. While this exchange contribution shows sample-to-sample fluctuations, it is for all QPCs correlated with the zero-field splitting of the 0.7 anomaly. This provides evidence that the splitting of the 0.7 anomaly is dominated by this field-independent exchange splitting.