Heavy Carriers and Non-Drude Optical Conductivity in MnSi

TL;DR

This study investigates the optical properties of MnSi across a broad energy range, revealing non-Drude behavior and frequency-dependent effective mass and scattering rates below 100 K, similar to cuprates and ruthenates.

Contribution

It provides the first comprehensive optical conductivity measurements of MnSi from meV to eV energies, showing non-Drude behavior and phenomenological modeling of its optical response.

Findings

Effective mass becomes strongly frequency dependent below 100 K.

Scattering rate exhibits a linear frequency dependence.

Optical conductivity fits a  power law similar to cuprates and ruthenates.

Abstract

Optical properties of the weakly helimagnetic metal MnSi have been determined in the photon energy range from 2 meV to 4.5 eV using the combination of grazing incidence reflectance at 80 degrees (2 meV to 0.8 eV) and ellipsometry (0.8 to 4.5 eV). As the sample is cooled below 100 K the effective mass becomes strongly frequency dependent at low frequencies, while the scattering rate developes a linear frequency dependence. The complex optical conductivity can be described by the phenomenological relation \sigma(\omega,T) \propto (\Gamma(T)+i\omega)^{-1/2} used for cuprates and ruthenates.