Hydrostaticity and hidden order: effects of experimental conditions on the temperature-pressure phase diagram of URu2Si2

TL;DR

This study shows that the observed phase transition in URu2Si2 depends on the hydrostaticity of the pressure medium used during measurements, affecting the interpretation of its temperature-pressure phase diagram.

Contribution

It demonstrates how different pressure media influence the hysteresis and phase transition behavior in URu2Si2, highlighting the importance of hydrostatic conditions in such experiments.

Findings

Hysteresis observed with Fluorinert media

No hysteresis with n-pentane/isoamyl alcohol medium

Hydrostatic conditions are crucial for accurate phase diagram interpretation

Abstract

The pressure-dependence of the hidden order phase transition of URu2Si2 is shown to depend sensitively upon the quality of hydrostatic pressure conditions during electrical resistivity measurements. Hysteresis in pressure is demonstrated for two choices of pressure medium: the commonly-used mixture of 1:1 Fluorinert FC70/FC77 and pure FC75. In contrast, no hysteresis is observed when the pressure medium is a 1:1 mixture of n-pentane/isoamyl alcohol, as it remains hydrostatic over the entire studied pressure range. Possible ramifications for the interpretation of the temperature-pressure phase diagram of URu2Si2 are discussed.