Scaling and the Metal-Insulator Transition in Si/SiGe Quantum Wells

TL;DR

This paper demonstrates a zero magnetic field metal-insulator transition in Si/SiGe quantum wells, driven by strong interactions, with evidence of a Coulomb gap and universal scaling in resistivity.

Contribution

It provides experimental evidence for a zero-field metal-insulator transition in SiGe quantum wells and identifies interaction-driven mechanisms.

Findings

Metal-insulator transition observed at zero magnetic field.

Evidence of a Coulomb gap in resistivity data.

Resistivity in the insulating phase scales universally.

Abstract

The existence of a metal-insulator transition at zero magnetic field in two- dimensional electron systems has recently been confirmed in high mobility Si-MOSFETs. In this work, the temperature dependence of the resistivity of gated Si/SiGe/Si quantum well structures has revealed a similar metal- insulator transition as a function of carrier density at zero magnetic field. We also report evidence for a Coulomb gap in the temperature dependence of the resistivity of the dilute 2D hole gas confined in a SiGe quantum well. In addition, the resistivity in the insulating phase scales with a single parameter, and is sample independent. These results are consistent with the occurrence of a metal-insulator transition at zero magnetic field in SiGe square quantum wells driven by strong hole-hole interactions.