Pressure and alloying effects on the metal to insulator transition in NiS{2-x}Se{x} studied by infrared spectroscopy

TL;DR

This study investigates how pressure and alloying affect the metal-insulator transition in NiS{2-x}Se{x} using infrared spectroscopy, revealing different microscopic mechanisms despite similar effects on the material's electronic state.

Contribution

It demonstrates that pressure and Se-alloying induce the metal-insulator transition via different microscopic pathways, challenging previous assumptions of a linear scaling relation.

Findings

Pressure and alloying both produce an anomalous metallic state.

Optical results differ from transport-based scaling relations.

Microscopic origins of the transitions are substantially different.

Abstract

The metal to insulator transition in the charge transfer NiS{2-x}Se{x} compound has been investigated through infrared reflectivity. Measurements performed by applying pressure to pure NiS2 (lattice contraction) and by Se-alloying (lattice expansion) reveal that in both cases an anomalous metallic state is obtained. We find that optical results are not compatible with the linear Se-alloying vs Pressure scaling relation previously established through transport, thus pointing out the substantially different microscopic origin of the two transitions.