Unchanged thermopower enhancement at the semiconductor-metal transition in correlated FeSb$_{2-x}$Te$_x$

TL;DR

This study shows that in FeSb$_{2-x}$Te$_x$, thermopower remains significantly enhanced across the semiconductor-metal transition, highlighting the role of electron correlations in thermal transport and potential for cryogenic thermoelectric applications.

Contribution

It demonstrates that thermopower enhancement persists unchanged through the semiconductor-metal transition in FeSb$_{2-x}$Te$_x$, emphasizing electron correlations' importance.

Findings

Thermopower enhancement is nearly constant across the transition.

An enhancement factor of 10-30 is needed for classical electron diffusion estimates.

Electron-electron correlations significantly influence thermal transport.

Abstract

Substitution of Sb in FeSb$_2$ by less than 0.5% of Te induces a transition from a correlated semiconductor to an unconventional metal with large effective charge carrier mass $m^*$. Spanning the entire range of the semiconductor-metal crossover, we observed an almost constant enhancement of the measured thermopower compared to that estimated by the classical theory of electron diffusion. Using the latter for a quantitative description one has to employ an enhancement factor of 10-30. Our observations point to the importance of electron-electron correlations in the thermal transport of FeSb$_2$, and suggest a route to design thermoelectric materials for cryogenic applications.