Collapse of antiferromagnetism in CeRh2Si2 : volume versus entropy

TL;DR

This study investigates the pressure-induced changes in antiferromagnetism and Fermi surface in CeRh2Si2, revealing anomalies and anisotropic effects near the quantum critical point, challenging the expected sharp transition.

Contribution

It provides new insights into the pressure dependence of antiferromagnetism and Fermi surface reconstruction in CeRh2Si2, highlighting anomalies and anisotropic behaviors near the quantum critical point.

Findings

Anomaly in thermal expansion persists above critical pressure.

Transition pressure dependence is slower than predicted for a first order transition.

Fermi surface reconstruction causes anisotropic transport responses.

Abstract

The thermal expansion of the heavy fermion compound CeRh2Si2 has been measured under pressure as a function of temperature using strain gages. A large anomaly associated to the Neel temperature has been detected even above the suspected critical pressure Pc = 1.05 GPa where no indication of antiferromagnetism has been observed in calorimetry experiments sensitive to the entropy change. An unexpected feature is the pressure slowdown of the antiferromagnetic-paramagnetic transition by comparison to the fast pressure collapse predicted for homogeneous first order quantum phase transition with one unique pressure singularity at Pc. A large pressure dependance is observed in the anisotropy of the thermal expansion measured parallel or perpendicular to the c axis of this tetragonal crystal. The Fermi surface reconstruction associated to the first order transition produces quite different pressure response in the transport scattering measured along different crystallographic directions. A brief discussion is made on other examples of first order quantum transitions in strongly correlated electronic systems : MnSi and CeCoIn5.