Commensurability oscillations in the rf conductivity of unidirectional lateral superlattices: measurement of anisotropic conductivity by coplanar waveguide

TL;DR

This study measures the anisotropic rf magnetoconductivity of unidirectional lateral superlattices using coplanar waveguides, revealing how microwave power influences the dominance of diffusion or collisional contributions in commensurability oscillations.

Contribution

It introduces a method to measure anisotropic conductivity in superlattices via microwave attenuation, highlighting power-dependent effects on oscillation behavior and electron-phonon scattering impacts.

Findings

Anisotropic commensurability oscillations observed at low microwave power.

High microwave power causes loss of directional selectivity in conductivity measurements.

Diffusion contribution dominates at low power, while large-angle electron-phonon scattering affects high-power results.

Abstract

We have measured the rf magnetoconductivity of unidirectional lateral superlattices (ULSLs) by detecting the attenuation of microwave through a coplanar waveguide placed on the surface. ULSL samples with the principal axis of the modulation perpendicular (S_perp) and parallel (S_||) to the microwave electric field are examined. For low microwave power, we observe expected anisotropic behavior of the commensurability oscillations (CO), with CO in samples S_perp and S_|| dominated by the diffusion and the collisional contributions, respectively. Amplitude modulation of the Shubnikov-de Haas oscillations is observed to be more prominent in sample S_||. The difference between the two samples is washed out with the increase of the microwave power, letting the diffusion contribution govern the CO in both samples. The failure of the intended directional selectivity in the conductivity measured with high microwave power is interpreted in terms of large-angle electron-phonon scattering.