Magnetoplasma excitations of two-dimensional anisotropic heavy fermions in AlAs quantum wells

TL;DR

This study investigates plasma and magnetoplasma excitations in anisotropic heavy fermion systems within AlAs quantum wells, revealing how electron density and valley population influence the plasma spectrum and inter-valley interactions.

Contribution

First experimental analysis of plasma excitations in anisotropic heavy fermions in AlAs quantum wells, highlighting valley-specific effects and electron density dependence.

Findings

Identified two distinct plasma resonances corresponding to different electron mass values.

Demonstrated that increasing electron density populates a second valley, altering the plasma spectrum.

Measured inter-valley splitting energy and electron densities in each valley.

Abstract

The spectra of plasma and magnetoplasma excitations in a two-dimensional system of anisotropic heavy fermions were investigated for the first time. The spectrum of microwave absorption by disk-like samples of stressed AlAs quantum wells at low electron densities showed two plasma resonances separated by a frequency gap. These two plasma resonances correspond to electron mass principle values of $(1.10 \pm 0.05) m_0$ and $(0.20 \pm 0.01) m_0$. The observed results correspond to the case of a single valley strongly anisotropic Fermi surface. It was established that electron density increase results in population of the second valley, manifesting itself as a drastic modification of the plasma spectrum. We directly determined the electron densities in each valley and the inter-valley splitting energy from the ratio of the two plasma frequencies.