BaVS$_3$ probed by V L edge X-ray absorption spectroscopy

TL;DR

This study uses polarization-dependent V L edge X-ray absorption spectroscopy to investigate phase-dependent electronic structure changes in BaVS$_3$, revealing pretransitional charge density wave fluctuations and local symmetry rearrangements.

Contribution

It provides new insights into the electronic and structural evolution of BaVS$_3$ across its phases using polarization-sensitive X-ray absorption spectroscopy.

Findings

Detection of temperature-dependent linear dichroism changes.

Observation of new pre-edge structures below the metal-insulator transition.

Evidence of charge density wave fluctuations preceding the transition.

Abstract

Polarization dependent vanadium L edge X-ray absorption spectra of BaVS$_3$ single crystals are measured in the four phases of the compound. The difference between signals with the polarization \textbf{E}$\perp$\textbf{c} and \textbf{E}$\parallel$\textbf{c} (linear dichroism) changes with temperature. Besides increasing intensity of one of the maxima, a new structure appears in the pre-edge region below the metal-insulator transition. More careful examination brings to light that the changes start already with pretransitional charge density wave fluctuations. Simple symmetry analysis suggests that the effect is related to rearrangements in $E_{g}$ and $A_{1g}$ states, and is compatible with the formation of four inequivalent V sites along the V-S chain.