Evidence for electron-phonon interaction in Fe$_{1-x}$M$_{x}$Sb$_{2}$ (M=Co, Cr) single crystals

TL;DR

This study uses polarized Raman scattering to investigate electron-phonon interactions in Fe$_{1-x}$M$_{x}$Sb$_{2}$ (M=Co, Cr) single crystals, revealing temperature-dependent coupling and effects of alloying.

Contribution

It provides experimental evidence of electron-phonon coupling in FeSb$_2$ derivatives and shows how alloying influences phonon modes and interactions.

Findings

Electron-phonon coupling peaks at about 40 K.

Alloying reduces electron-phonon interaction strength.

Mode broadening is due to anharmonic effects.

Abstract

We have measured polarized Raman scattering spectra of the Fe$_{1-x}$Co$_{x}$Sb$_{2}$ and Fe$_{1-x}$Cr$_{x}$Sb$_{2}$ (0$\leq x\leq $0.5) single crystals in the temperature range between 15 K and 300 K. The highest energy $B_{1g}$ symmetry mode shows significant line asymmetry due to phonon mode coupling width electronic background. The coupling constant achieves the highest value at about 40 K and after that it remains temperature independent. Origin of additional mode broadening is pure anharmonic. Below 40 K the coupling is drastically reduced, in agreement with transport properties measurements. Alloying of FeSb$_2$ with Co and Cr produces the B$_{1g}$ mode narrowing, i.e. weakening of the electron-phonon interaction. In the case of A$_{g}$ symmetry modes we have found a significant mode mixing.