Quantum-Classical Crossover and Apparent Metal-Insulator Transition in a Weakly Interacting 2D Fermi Liquid

TL;DR

This paper observes a magnetic field-induced metal-insulator transition in a high-mobility 2D electron gas, explained as a quantum-classical crossover driven by magneto-orbital coupling rather than spin or localization effects.

Contribution

It demonstrates a new type of transition in 2D electron systems caused by magneto-orbital effects, not spin or disorder, expanding understanding of 2D metal-insulator phenomena.

Findings

Metal-insulator transition induced by magnetic field in 2DEG.

High-mobility metallic phase aligns with Fermi liquid theory.

Insulating phase shows strong negative temperature dependence.

Abstract

We report the observation of a parallel magnetic field induced metal-insulator transition (MIT) in a high-mobility two-dimensional electron gas (2DEG) for which spin and localization physics most likely play no major role. The high-mobility metallic phase at low field is consistent with the established Fermi liquid transport theory including phonon scattering, whereas the insulating phase at higher field shows a large negative temperature dependence at resistances much smaller than the quantum of resistance, $h/e^2$. We argue that this observation is a direct manifestation of a quantum-classical crossover arising predominantly from the magneto-orbital coupling between the finite width of the 2DEG and the in-plane magnetic field.