Direct observation of double valence-band extrema and anisotropic effective masses of the thermoelectric material SnSe

TL;DR

This study uses advanced spectroscopy to reveal the detailed electronic structure of SnSe, showing double valence-band extrema and anisotropic effective masses, which are crucial for improving its thermoelectric efficiency.

Contribution

First direct observation of double valence-band maxima and anisotropic effective masses in SnSe using angle-resolved photoemission spectroscopy.

Findings

Identification of two nearly independent hole bands with a 20 meV energy difference.

Anisotropic effective masses with in-plane values of 0.16-0.39 m₀ and out-of-plane of 0.71 m₀.

Electronic structure insights to guide thermoelectric performance enhancement.

Abstract

Synchrotron-based angle-resolved photoemission spectroscopy is used to determine the electronic structure of layered SnSe, which was recently turned out to be a potential thermoelectric material. We observe that the top of the valence band consists of two nearly independent hole bands, whose tops differ by ~20 meV in energy, indicating the necessity of a multivalley model to describe the thermoelectric properties. The estimated effective masses are anisotropic, with in-plane values of 0.16-0.39 m$_0$ and an out-of-plane value of 0.71 m$_0$, where m$_0$ is the rest electron mass. Information of the electronic structure is essential to further enhance the thermoelectric performance of hole-doped SnSe.