Pressure-Induced Re-entrant transition in NbS3 Phases: Combined Raman Scattering and X-ray Diffraction Study

TL;DR

This study investigates how pressure affects charge density wave states in NbS3 phases using Raman and X-ray diffraction, revealing a transition from insulating to metallic states and subsequent charge orderings.

Contribution

It provides the first combined Raman and X-ray diffraction analysis of pressure-induced phase transitions in NbS3, highlighting re-entrant charge density wave behavior.

Findings

Charge density waves are suppressed around 6-8 GPa.

A transition from insulating to metallic state occurs under pressure.

New charge orderings emerge above 8 GPa.

Abstract

We report the evolution of charge density wave states under pressure for two NbS3 phases triclinic (phase I) and monoclinic (phase II) at room temperature. Raman and X-ray diffraction (XRD) techniques are applied. The x-ray studies on the monoclinic phase under pressure show a compression of the lattice at different rates below and above 7 GPa but without a change in space group symmetry. The Raman spectra of the two phases evolve similarly with pressure; all peaks almost disappear in the 6-8 GPa range, indicating a transition from an insulating to a metallic state, and peaks at new positions appear above 8 GPa. The results suggest suppression of the ambient charge-density waves and their subsequent recovery with new orderings above 8 GPa.