Experimental evidence of a metal-insulator transition in a half-filled Landau level

TL;DR

This study provides experimental evidence of a metal-insulator transition at a half-filled Landau level in a high-mobility GaAs/AlGaAs heterostructure, showing a disorder-induced crossover from metallic to insulating states.

Contribution

First experimental demonstration of a disorder-driven metal-insulator transition at a half-filled Landau level in a high-mobility heterostructure, supporting composite fermion theory.

Findings

Observation of metallic to insulating crossover at ν=1/2 with increasing disorder

Comparison of experimental results with theoretical predictions

Control of disorder via gate voltage in high-mobility heterostructures

Abstract

We have measured the low-temperature transport properties of a high-mobility front-gated GaAs/Al_{0.33}Ga_{0.67}As heterostructure. By changing the applied gate voltage, we can vary the amount of disorder within the system. At a Landau level filling factor $\nu =1/2$, where the system can be described by the composite fermion picture, we observe a crossover from metallic to insulating behaviour as the disorder is increased. Experimental results and theoretical prediction are compared.