Orbital Magnetization Measurement of the Quantum Hall to Insulator Transition

TL;DR

This study measures orbital magnetization in a 2D electron gas to detect the quantum Hall to insulator transition, revealing an unexpected thermodynamic signature at the critical point.

Contribution

It provides the first direct magnetization measurement of the QH-I transition, uncovering a sharp change at the critical point in a disordered GaAs/AlGaAs system.

Findings

Abrupt magnetization change at the transition point

Observation of de Haas-van Alphen-like oscillations

Thermodynamic signature of a second order quantum phase transition

Abstract

We present a magnetization measurement probing the transition from a quantum Hall to insulating (QH-I) state for a two-dimensional electron gas in a disordered GaAs/AlGaAs heterostructure. Using a highly sensitive DC torque magnetometer, we discover an abrupt change in the orbital magnetization precisely at the critical point for the QH-I transition. Since this transition is predicted to be a second order quantum phase transition, a thermodynamic signature in magnetization is totally unexpected. The observed feature is reminiscent of the well-known de Haas-van Alphen oscillations arising from discontinuous jumps of the chemical potential as Landau Levels are successively populated.