Energy-level pinning and the 0.7 spin state in one dimension: GaAs quantum wires studied using finite-bias spectroscopy

TL;DR

This study investigates electron interactions in GaAs quantum wires, revealing how energy levels pin to the chemical potential and rearrange at crossings, explaining the 0.7 conductance anomaly and related phenomena.

Contribution

It provides direct experimental evidence of spin-level pinning and rearrangement in 1D quantum wires, elucidating the origin of the 0.7 structure and magnetic phase transitions.

Findings

Spin-up levels pin to the chemical potential during population.

Energy levels rearrange abruptly at crossing points.

The results explain the 0.7 conductance anomaly.

Abstract

We study the effects of electron-electron interactions on the energy levels of GaAs quantum wires (QWs) using finite-bias spectroscopy. We probe the energy spectrum at zero magnetic field, and at crossings of opposite-spin-levels in high in-plane magnetic field B. Our results constitute direct evidence that spin-up (higher energy) levels pin to the chemical potential as they populate. We also show that spin-up and spin-down levels abruptly rearrange at the crossing in a manner resembling the magnetic phase transitions predicted to occur at crossings of Landau levels. This rearranging and pinning of subbands provides a phenomenological explanation for the 0.7 structure, a one-dimensional (1D) nanomagnetic state, and its high-B variants.