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

摘要

We study the effects of electron-electron interactions on the energy levelsof GaAs quantum wires (QWs) using finite-bias spectroscopy. We probe the energyspectrum at zero magnetic field, and at crossings of opposite-spin-levels inhigh in-plane magnetic field B. Our results constitute direct evidence thatspin-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 thecrossing in a manner resembling the magnetic phase transitions predicted tooccur at crossings of Landau levels. This rearranging and pinning of subbandsprovides a phenomenological explanation for the 0.7 structure, aone-dimensional (1D) nanomagnetic state, and its high-B variants.