Topological Phase Diagram of a Two-Subband Electron System

TL;DR

This paper maps the phase diagram of a two-subband 2D electron system, revealing novel topological features and evidence of reentrant quantum Hall transitions through experimental measurements.

Contribution

It provides the first detailed experimental phase diagram of a two-subband electron system showing anomalous topology and reentrant quantum Hall states.

Findings

Distinct topology from conventional Landau fan diagram

Regions of negative differential Hall resistance

Evidence of reentrant quantum Hall transitions

Abstract

We present a phase diagram for a two-dimensional electron system with two populated subbands. Using a gated GaAs/AlGaAs single quantum well, we have mapped out the phases of various quantum Hall states in the density-magnetic filed plane. The experimental phase diagram shows a very different topology from the conventional Landau fan diagram. We find regions of negative differential Hall resistance which are interpreted as preliminary evidence of the long sought reentrant quantum Hall transitions. We discuss the origins of the anomalous topology and the negative differential Hall resistance in terms of the Landau level and subband mixing.