Hall field-induced resistance oscillations in a tunable-density GaAs quantum well

TL;DR

This study investigates Hall field-induced resistance oscillations in a tunable GaAs quantum well, revealing how subband population affects HIRO frequency and electron quantum lifetime, with significant enhancement in the two-subband regime.

Contribution

It demonstrates the impact of second subband population on HIRO behavior and electron lifetime in a tunable GaAs quantum well, revealing new density-dependent phenomena.

Findings

HIRO frequency scales as n^{-1/2} at low density

Population of the second subband enhances HIRO amplitude

Quantum lifetime of SB1 electrons reaches 52 ps in the two-subband regime

Abstract

We report on Hall field-induced resistance oscillations (HIRO) in a 60 nm-wide GaAs/AlGaAs quantum well with an \emph{in situ} grown back gate, which allows tuning the carrier density $n$. At low $n$, when all electrons are confined to the lowest subband (SB1), the HIRO frequency, proportional to the product of the cyclotron diameter and the Hall field, scales with $n^{-1/2}$, as expected. Remarkably, population of the second subband (SB2) significantly enhances HIRO, while their frequency now scales as $n^{-1}$. We demonstrate that in this two-subband regime HIRO still originate solely from backscattering of SB1 electrons. The unusual density dependence occurs because the population of SB2 steadily increases, while that of SB1 remains essentially unchanged. The enhancement of HIRO manifests an unexpected, step-like increase of the quantum lifetime of SB1 electrons, which reaches a record value of 52 ps in the two-subband regime.