Anisotropic Correlated Electronic Structure of Colossal Thermopower Marcasite FeSb$_2$

TL;DR

This study combines ARPES and first-principles calculations to reveal the anisotropic, correlated electronic structure of FeSb$_2$, providing insights into its colossal thermopower phenomenon.

Contribution

It offers a detailed microscopic understanding of FeSb$_2$'s electronic structure, highlighting the role of anisotropy and electron correlations in its thermoelectric properties.

Findings

Identification of two key bands near the Fermi level in FeSb$_2$

Revelation of strong electron correlations among Fe-3d states

Discovery of significant anisotropy in the electronic structure

Abstract

Iron antimonide (FeSb$_2$) is a mysterious material with peculiar colossal thermopower of about $-45$ mV/K at 10 K. However, a unified microscopic description of this phenomenon is far from being achieved. The understanding of the electronic structure in details is crucial in identifying the microscopic mechanism of FeSb$_2$ thermopower. Combining angle-resolved photoemission spectroscopy (ARPES) and first-principles calculations we find that the spectrum of FeSb$_2$ consists of two bands near the Fermi energy: the nondispersive strongly renormalized $\alpha$-band, and the hole-like $\beta$-band that intersects the first one at $\Gamma$ and Y points of the Brillouin zone. Our study reveals the presence of sizable correlations, predominantly among electrons derived from Fe-3d states, and considerable anisotropy in the electronic structure of FeSb$_2$. These key ingredients are of fundamental importance in the description of colossal thermopower in FeSb$_2$.