Experimental consequences at high temperatures of quantum critical points

TL;DR

This paper investigates how quantum critical points influence high-temperature phase transitions in Cr-Re alloys, revealing a universal crossover criterion and explaining the material's high-temperature quantum effects.

Contribution

It introduces a general criterion for the crossover from thermal to quantum fluctuation dominance, applicable to materials with low coherence lengths.

Findings

The antiferromagnetic transition temperature follows a (x_c-x)/x_c)^{1/2} law up to 600K.

Quantum critical effects are observable at unusually high temperatures in this system.

A universal criterion for the thermal-quantum crossover is proposed.

Abstract

We study the Cr_(1-x) Re_x phase diagram finding that its phase transition temperature towards an antiferromagnetic order T_N follows a quantum [(x_c-x)/x_c ]^{\psi} law, with {\psi}=1/2, from the quantum critical point (QCP) at x_c=0.25 up to T_N=600K. We compare this system to others in order to understand why this elemental material is affected by the QCP up to such unusually high temperatures. We determine a general criterion for the crossover, as function of an external parameter such as concentration, from the region controlled solely by thermal fluctuations to that where quantum effects become observable. The properties of materials with low coherence lengths will thus be altered far away from the QCP.