Pressure induced electronic transitions in Samarium monochalcogenides

TL;DR

This study uses dynamical mean field theory to accurately model pressure-induced insulator-metal transitions in Samarium monochalcogenides, revealing the nature of electronic phases and improving prediction of material properties.

Contribution

It demonstrates the importance of charge and spin fluctuations in modeling electronic transitions, providing new insights into the correlated band insulator behavior of Sm-monochalcogenides.

Findings

Identification of intermediate valence states at high pressure

Improved predictions of lattice constants and bulk moduli

Classification of transitions as correlated band insulators

Abstract

Pressure induced isostructural insulator to metal transition for SmS is characterised by the presence of an intermediate valence state at higher pressure which cannot be captured by the density functional theory. As a direct outcome of including the charge and spin fluctuations incorporated in dynamical mean field theory, we see the emergence of insulating and metallic phases with increasing pressure as a function of changing valence. This is accompanied by significantly improved predictions of the equilibrium lattice constants and bulk moduli for all Sm-monochalcogenides verifying experiments. Nudged Elastic Band analysis reveals the insulating states to have a finite quasiparticle weight, decreasing as the gap closes rendering the transition to be not Mott-like, and classifies these materials as correlated band insulators. The difference between the discontinuous and continuous natures of these transitions can be attributed to the closeness of the sharply resonant Sm-4f peaks to the fermi level in the predicted metallic states in SmS as compared to SmSe and SmTe.