Deformed Fermi Surface Theory of Magneto-Acoustic Anomaly in Modulated Quantum Hall Systems Near $/nu=1/2$

TL;DR

This paper proposes a deformed composite fermion Fermi surface model to explain anisotropic magneto-acoustic anomalies observed in modulated quantum Hall systems near filling factor 1/2, aligning well with experimental data.

Contribution

It introduces a new generic model of a deformed CF-FS that accounts for anisotropic anomalies in sound velocity and attenuation in modulated quantum Hall systems.

Findings

Model explains anisotropic anomalies in sound velocity and attenuation.

Calculated dependencies match experimental observations.

Regions of flattened CF-FS contribute to conductivity tensor effects.

Abstract

We introduce a new generic model of a deformed Composite Fermion-Fermi Surface (CF-FS) for the Fractional Quantum Hall Effect near $/nu=1/2$ in the presence of a periodic density modulation. Our model permits us to explain recent Surface Acoustic Wave observations of anisotropic anomalies [1,2] in sound velocity and attenuation- appearance of peaks and anisotropy - which originate from contributions to the conductivity tensor due to regions of the CF-FS which are flattened by the applied modulation. The calculated magnetic field and wave vector dependence of the CF conductivity,velocity shift and attenuation agree with experiments.