Dynamic Nuclear Polarization in a Quantum Hall Corbino Disk

TL;DR

This study investigates how electrical polarization of nuclear spins occurs in a Corbino disk during quantum Hall effect breakdown, revealing that bulk current, not edge channels, drives dynamic nuclear polarization.

Contribution

It demonstrates that DNP in a Corbino disk is induced by bulk current during QHE breakdown, highlighting a new mechanism distinct from edge channel effects.

Findings

DNP occurs near the critical voltage of QHE breakdown

Bulk current is responsible for DNP in the absence of edge channels

DNP onset aligns with QHE breakdown voltage

Abstract

Electrical polarization of nuclear spins is studied in a Corbino disk under a breakdown regime of the quantum Hall effect (QHE). Since the edge channels are completely absent in the Corbino disk, we conclude that the electric current flowing in the bulk channel of a quantum Hall conductor is relevant to dynamic nuclear polarization (DNP). A pump and probe measurement demonstrates that DNP emerges near the critical voltage of the QHE breakdown. The agreement of the onset voltage of DNP with that of the QHE breakdown indicates that the underlying origin of DNP is closely related to that of the QHE breakdown.