Giant low-temperature piezoresistance effect in AlAs two-dimensional electrons

TL;DR

This study reveals an exceptionally large low-temperature piezoresistance effect in AlAs two-dimensional electrons, with gauge factors exceeding 10,000 and reaching 56,000 under magnetic fields, explained by intervalley charge transfer.

Contribution

It reports the discovery of giant low-temperature piezoresistance in AlAs 2D electrons and provides a qualitative model based on intervalley charge transfer.

Findings

Gauge factors exceed 10,000 at low temperatures.

Gauge factors up to 56,000 with magnetic field.

Piezoresistance explained by intervalley charge transfer.

Abstract

We present piezoresistance measurements in modulation doped AlAs quantum wells where the two-dimensional electron system occupies two conduction band valleys with elliptical Fermi contours. Our data demonstrate that, at low temperatures, the strain gauge factor (the fractional change in resistance divided by the sample's fractional length change) in this system exceeds 10,000. Moreover, in the presence of a moderate magnetic field perpendicular to the plane of the two-dimensional system, gauge factors up to 56,000 can be achieved. The piezoresistance data can be explained qualitatively by a simple model that takes into account intervalley charge transfer.