Large isotropic negative thermal expansion above a structural quantum phase transition

TL;DR

This study reveals that the simple cubic perovskite ScF3 exhibits large isotropic negative thermal expansion driven by proximity to a quantum phase transition, with significant effects observed well above the transition temperature.

Contribution

It demonstrates the influence of a quantum phase transition on thermal and lattice properties in a simple perovskite, highlighting effects above the transition temperature.

Findings

Signatures of approaching a quantum phase transition in ScF3.

Strong effects on physical properties observed up to 100 K above the transition.

Correlations in the cubic phase are influenced by the transition.

Abstract

Perovskite structured materials contain myriad tunable ordered phases of electronic and magnetic origin with proven technological importance and strong promise for a variety of energy solutions. An always-contributing influence beneath these cooperative and competing interactions is the lattice, whose physics may be obscured in complex perovskites by the many coupled degrees of freedom which makes these systems interesting. Here we report signatures of an approach to a quantum phase transition very near the ground state of the nonmagnetic, ionic insulating, simple cubic perovskite material ScF3 and show that its physical properties are strongly effected as much as 100 K above the putative transition. Spatial and temporal correlations in the high-symmetry cubic phase determined using energy- and momentum-resolved inelastic X-ray scattering as well as X-ray diffraction reveal that soft mode, central peak and thermal expansion phenomena are all strongly influenced by the transition.