Correlated electronic structure and optical response of rare-earth-based semiconductors

TL;DR

This paper combines advanced theoretical methods to analyze the complex optical responses of rare-earth semiconductors, revealing unique electronic transitions and anisotropic properties aligned with experimental observations.

Contribution

It introduces a combined dynamical mean-field and semi-local exchange-correlation approach to accurately model optical properties of rare-earth semiconductors from first principles.

Findings

SmSF absorption edge from S-3p to Sm-4f transitions

GdSF behaves as a typical p-d gap semiconductor

PrSF and NdSF show hybridized 4f-5d states at conduction band bottom

Abstract

Simultaneous occurrence of the Mott and band gap in correlated semiconductors results in a complex optical response with the nature of the absorption edge difficult to resolve both experimentally and theoretically. Here, we combine a dynamical mean-field theory approach to localized 4f shells with an improved description of band gaps by a semi-local exchange-correlation potential to calculate the optical properties of the light rare-earth fluorosulfides LnSF (Ln=Pr, Nd, Sm, Gd) from first principles. In agreement with experiment, we find the absorption edge in SmSF to stem from S-3p to Sm-4f transitions, while the Gd compound behaves as an ordinary p-d gap semiconductor. In the unexplored PrSF and NdSF systems we predict a rather unique occurrence of strongly hybridized 4f-5d states at the bottom of the conduction band. The nature of the absorption edge underlies a peculiar anisotropy of the optical conductivity in each system.