Dynamic nuclear polarization and Knight shift measurements in a breakdown regime of integer quantum Hall effect

TL;DR

This paper investigates how nuclear spins are polarized electrically during the breakdown of the integer quantum Hall effect, revealing their influence on spin-splitting energy and QHE breakdown, with measurements of the Knight shift.

Contribution

It demonstrates electrical nuclear spin polarization and measures the Knight shift in a quantum Hall breakdown regime, providing new insights into spin interactions in this system.

Findings

Nuclear spins are polarized electrically during QHE breakdown

Polarized nuclear spins reduce spin-splitting energy

Knight shift measurements reveal electron-nuclear spin interactions

Abstract

Nuclear spins are polarized electrically in a breakdown regime of an odd-integer quantum Hall effect (QHE). Electron excitation to the upper Landau subband with the opposite spin polarity flips nuclear spins through the hyperfine interaction. The polarized nuclear spins reduce the spin-splitting energy and accelerate the QHE breakdown. The Knight shift of the nuclear spins is also measured by tuning electron density during the irradiation of radio-frequency magnetic fields.