Pressure-induced enhancement of non-polar to polar transition temperature in metallic LiOsO$_3$

TL;DR

This study demonstrates that applying pressure increases the transition temperature from non-polar to polar in LiOsO₃, reaching about 250 K at 6.5 GPa, due to the polar phase's smaller volume being stabilized.

Contribution

It combines experimental transport measurements with first-principles calculations to show pressure enhances the polar transition temperature in LiOsO₃, revealing volume effects on structural stability.

Findings

Transition temperature $T_s$ increases with pressure.

Polar $R3c$ structure is stabilized by pressure.

$T_s$ reaches ~250 K at 6.5 GPa.

Abstract

LiOsO$_3$ undergoes a continuous transition from a centrosymmetric $R\bar{3}c$ structure to a polar $R3c$ structure at $T_s=140$~K. By combining transport measurements and first-principles calculations, we find that $T_s$ is enhanced by applied pressure, and it reaches a value of $\sim$250~K at $\sim$6.5~GPa. The enhancement is due to the fact that the polar $R3c$ structure of LiOsO$_3$ has a smaller volume than the centrosymmetric $R\bar{3}c$ structure. Pressure generically favors the structure with the smallest volume, and therefore further stabilizes the polar $R3c$ structure over the $R\bar{3}c$ structure, leading to the increase in $T_s$.