Linear magnetoresistance in a quasi-free two dimensional electron gas in an ultra-high mobility GaAs quantum well

TL;DR

This study demonstrates a strong linear magnetoresistance in ultra-high mobility GaAs quantum wells, revealing insights into quantum oscillations and transport mechanisms in a simple, single-subband electron system across a wide temperature range.

Contribution

It provides the first detailed magnetotransport analysis of ultra-high mobility GaAs quantum wells showing linear magnetoresistance and its relation to quantum oscillations and the empirical resistance rule.

Findings

Observation of linear magnetoresistance up to 10^5%

Quantum oscillations superimposed at low temperatures

Validation of the empirical resistance rule across temperatures

Abstract

We report a magnetotransport study of an ultra-high mobility ($\bar{\mu}\approx 25\times 10^6$\,cm$^2$\,V$^{-1}$\,s$^{-1}$) $n$-type GaAs quantum well up to 33 T. A strong linear magnetoresistance (LMR) of the order of 10$^5$ % is observed in a wide temperature range between 0.3 K and 60 K. The simplicity of our material system with a single sub-band occupation and free electron dispersion rules out most complicated mechanisms that could give rise to the observed LMR. At low temperature, quantum oscillations are superimposed onto the LMR. Both, the featureless LMR at high $T$ and the quantum oscillations at low $T$ follow the empirical resistance rule which states that the longitudinal conductance is directly related to the derivative of the transversal (Hall) conductance multiplied by the magnetic field and a constant factor $\alpha$ that remains unchanged over the entire temperature range. Only at low temperatures, small deviations from this resistance rule are observed beyond $\nu=1$ that likely originate from a different transport mechanism for the composite fermions.