Uniform structural phase transition in V$_2$O$_3$ without short-range distortions of the local structure

TL;DR

This study reveals that V$_2$O$_3$ undergoes a uniform structural phase transition without local distortions, indicating the lattice plays a secondary role compared to magnetic fluctuations in the metal-insulator transition.

Contribution

The paper provides direct local structural evidence showing the absence of short-range distortions in V$_2$O$_3$ during the phase transition, challenging previous assumptions about local distortions.

Findings

No monoclinic local distortions above transition

Phase coexistence observed between 150 K and 160 K

Lattice fluctuations are not primary in transition mechanism

Abstract

The local structure of V$_{2}$O$_{3}$, an archetypal strongly correlated electron system that displays a metal-insulator transition around 160 K, has been investigated via pair distribution function (PDF) analysis of neutron and x-ray total scattering data. The rhombohedral-to-monoclinic structural phase transition manifests as an abrupt change on all length scales in the observed PDF. No monoclinic distortions of the local structure are found above the transition, although coexisting regions of phase-separated rhombohedral and monoclinic symmetry are observed between 150 K and 160 K. This lack of structural fluctuations above the transition contrasts with the known presence of magnetic fluctuations in the high-temperature state, suggesting that the lattice degree of freedom plays a secondary role behind the spin degree of freedom in the transition mechanism.