Temperature Induced Transitions between Insulator, Metal, and Quantum Hall States

TL;DR

This study observes temperature-driven phase transitions in a high mobility 2D silicon electron system, revealing insulator, metal, and quantum Hall states as temperature varies, especially near the $ u=1$ quantum Hall effect.

Contribution

It demonstrates temperature-induced transitions between different electronic phases in a dilute 2D electron system, highlighting the dynamic behavior of extended states near the quantum Hall regime.

Findings

Extended states sink below the Fermi level as temperature decreases.

Quantum Hall effect appears at low temperatures.

Conductivity shows metallic behavior when extended states cross the Fermi level.

Abstract

We report the observation of TEMPERATURE-INDUCED transitions between insulator, metal, and quantum-Hall behaviors for transport coefficients in the very dilute high mobility two-dimensional electron system in silicon. We consider the $\nu=1$ quantum Hall effect at the border of it's existence, at very low electron density. Our data show that as the temperature decreases, the extended states at $\nu=1$ (above the Fermi level at higher temperature so that the system behaves as an insulator) sink below the Fermi energy, so that the quantum Hall effect occurs. As the extended states cross the Fermi level, the conductivity has a temperature dependence characteristic of a metallic system.