Electronic correlations in the semiconducting half-Heusler compound FeVSb

TL;DR

This study reveals that electronic correlations, typically negligible in insulators, significantly affect the band structure of FeVSb, a semiconducting half-Heusler compound, through mass renormalization consistent with many-body theories.

Contribution

It demonstrates the presence of notable electronic correlations in a band insulator, challenging the conventional view that correlations are insignificant in such materials.

Findings

Measured a mass renormalization of 1.4 in FeVSb.

Quantitative agreement between ARPES and DMFT calculations.

Highlights the role of Hund's coupling in intermetallic band insulators.

Abstract

Electronic correlations are crucial to the low energy physics of metallic systems with localized $d$ and $f$ states; however, their effect on band insulators and semiconductors is typically negligible. Here, we measure the electronic structure of the half-Heusler compound FeVSb, a band insulator with filled shell configuration of 18 valence electrons per formula unit ($s^2 p^6 d^{10}$). Angle-resolved photoemission spectroscopy (ARPES) reveals a mass renormalization of $m^{*}/m_{bare}= 1.4$, where $m^{*}$ is the measured effective mass and $m_{bare}$ is the mass from density functional theory (DFT) calculations with no added on-site Coulomb repulsion. Our measurements are in quantitative agreement with dynamical mean field theory (DMFT) calculations, highlighting the many-body origin of the mass renormalization. This mass renormalization lies in dramatic contrast to other filled shell intermetallics, including the thermoelectric materials CoTiSb and NiTiSn; and has a similar origin to that in FeSi, where Hund's coupling induced fluctuations across the gap can explain a dynamical self-energy and correlations. Our work calls for a re-thinking of the role of correlations and Hund's coupling in intermetallic band insulators.