Interaction of surface acoustic waves with a two-dimensional electron gas in the presence of spin splitting of the Landau bands

TL;DR

This study investigates how surface acoustic waves interact with a two-dimensional electron gas in GaAs/AlGaAs heterostructures, revealing effects of spin splitting of Landau levels on wave absorption and velocity.

Contribution

It provides new measurements of the g factor and Landau band widths considering spin splitting effects in 2D electron systems under magnetic fields.

Findings

Determined effective g factor g* ≈ 5.

Measured spin-split Landau band width A ≈ 0.6 meV.

Observed nonlinear effects in SAW absorption related to spin splitting.

Abstract

The absorption and variation of the velocity of a surface acoustic wave of frequency $f$= 30 MHz interacting with two-dimensional electrons are investigated in GaAs/AlGaAs heterostructures with an electron density $n=(1.3 - 2.8) \times 10^{11} cm^{-2}$ at $T$=1.5 - 4.2 K in magnetic fields up to 7 T. Characteristic features associated with spin splitting of the Landau level are observed. The effective g factor and the width of the spin-split Landau bands are determined: $g^* \simeq 5$ and $A$=0.6 meV. The greater width of the orbital-split Landau bands (2 meV) relative to the spin-split bands is attributed to different shielding of the random fluctuation potential of charged impurities by 2D electrons. The mechanisms of the nonlinearities manifested in the dependence of the absorption and the velocity increment of the SAW on the SAW power in the presence of spin splitting of the Landau levels are investigated.