Optical evidence for heavy charge carriers in FeGe

TL;DR

This study uses optical spectroscopy to reveal heavy charge carriers and strong electron correlations in FeGe, showing significant mass renormalization and complex interband transitions.

Contribution

It provides the first detailed optical analysis of FeGe, demonstrating the presence of heavy quasi-particles and Coulomb interaction effects in this cubic helimagnetic metal.

Findings

Observation of a low energy interband transition at 0.22 eV

Identification of a narrow free carrier response with strong temperature dependence

Mass renormalization factor of approximately 12 indicating heavy quasiparticles

Abstract

The optical spectrum of the cubic helimagnetic metal FeGe has been investigated in the frequency range from 0.01 - 3.1 eV for different temperatures from 30 K to 296 K. The optical conductivity shows the evolution of a low energy (0.22 eV) interband transition and the development of a narrow free carrier response with a strong energy and temperature dependence. The frequency dependent effective mass and scattering rate derived from the optical data indicate the formation of dressed quasi-particles with a mass renormalization factor of 12. Similar to FeSi the spectral weight in FeGe is not recovered over a broad frequency range, an effect usually attributed to the influence of the on-site Coulomb interaction.