Minimum Metallic Mobility in a Two-Dimensional Electron Gas

TL;DR

This study observes a metal-insulator transition in a silicon-based two-dimensional electron gas, showing that increased mobility induces metallic behavior likely driven by electron-electron interactions, with magnetic field effects linked to spin interactions.

Contribution

First experimental demonstration of a mobility-controlled metal-insulator transition in 2D silicon electron gases, highlighting the role of electron-electron interactions and spin effects.

Findings

Metal-insulator transition occurs at mobility > 1 m^2/Vs.

Magnetoconductance is positive near the transition, negative elsewhere.

Transition behavior linked to spin-dependent electron interactions.

Abstract

We report the observation of a metal-insulator transition in a two-dimensional electron gas in silicon. By applying substrate bias, we have varied the mobility of our samples, and observed the creation of the metallic phase when the mobility was high enough ($\mu ~> 1 m^2/Vs$), consistent with the assertion that this transition is driven by electron-electron interactions. In a perpendicular magnetic field, the magnetoconductance is positive in the vicinity of the transition, but negative elsewhere. Our experiment suggests that such behavior results from a decrease of the spin-dependent part of the interaction in the vicinity of the transition.