Nernst effect in semi-metals: the meritorious heaviness of electrons

TL;DR

This paper investigates the Nernst effect in elemental Bismuth, revealing that its large Nernst coefficient results from low carrier density and long mean-free-path, highlighting potential for thermomagnetic cooling.

Contribution

It demonstrates that the large Nernst effect in Bismuth is due to electron properties, and suggests heavy-electron semi-metals as promising for low-temperature thermomagnetic applications.

Findings

Bismuth exhibits a Nernst coefficient larger than correlated metals.

Low carrier density and long mean-free-path drive the large Nernst effect.

Heavy-electron semi-metals could be effective for thermomagnetic cooling.

Abstract

We present a study of electric, thermal and thermoelectric transport in elemental Bismuth, which presents a Nernst coefficient much larger than what was found in correlated metals. We argue that this is due to the combination of an exceptionally low carrier density with a very long electronic mean-free-path. The low thermomagnetic figure of merit is traced to the lightness of electrons. Heavy-electron semi-metals, which keep a metallic behavior in presence of a magnetic field, emerge as promising candidates for thermomagnetic cooling at low temperatures.