Insulating state and giant non-local response in an InAs/GaSb quantum well in the quantum Hall regime

TL;DR

This study investigates the insulating state and significant non-local electrical responses in InAs/GaSb quantum wells under quantum Hall conditions, revealing complex edge-bulk interactions.

Contribution

It introduces a model explaining the coexistence of high local resistance and strong non-local signals via counter-propagating edge channels with residual bulk conductivity.

Findings

Observation of insulating behavior at electron-hole crossover with high magnetic fields

Detection of large non-local resistance signals comparable to local resistance

Proposed model of dissipative edge channels with residual bulk conduction

Abstract

We present transport measurements performed in InAs/GaSb double quantum wells. At the electron-hole crossover tuned by a gate voltage, a strong increase in the longitudinal resistivity is observed with increasing perpendicular magnetic field. Concomitantly with a local resistance exceeding the resistance quantum by an order of magnitude, we find a pronounced non-local resistance signal of almost similar magnitude. The co-existence of these two effects is reconciled in a model of counter-propagating and dissipative quantum Hall edge channels providing backscattering, shorted by a residual bulk conductivity.