Mid-infrared Hall effect in thin-film metals: Probing the Fermi surface anisotropy in Au and Cu

TL;DR

This paper introduces a sensitive mid-infrared technique to measure the complex Hall conductivity in thin Au and Cu films, revealing Fermi surface anisotropy effects through Hall scattering rates at low temperatures.

Contribution

It presents a novel MIR polarization modulation method to probe Fermi surface anisotropy via Hall effect measurements in thin metal films.

Findings

Hall frequency matches band theory predictions

First measurement of MIR Hall scattering rate in metals

Discrepancy between Hall and Drude scattering rates explained by Fermi surface anisotropy

Abstract

A sensitive mid-infrared (MIR, 900-1100 cm-1, 112-136 meV) photo-elastic polarization modulation technique is used to measure simultaneously Faraday rotation and circular dichroism in thin metal films. These two quantities determine the complex AC Hall conductivity. This novel technique is applied to study Au and Cu thin films at temperatures down to 20 K and magnetic fields up to 8 T. The Hall frequency is consistent with band theory predictions. We report the first measurement of the MIR Hall scattering rate, which is significantly lower than that derived from Drude analysis of zero magnetic field MIR transmission measurements. This difference is qualitatively explained in terms of the anisotropy of the Fermi surface in Au and Cu.