Quantum criticality and Lifshitz transition in the Ising system CeRu2Si2: Comparison with YbRh2Si2

TL;DR

This paper investigates Fermi surface instabilities and Lifshitz transitions near quantum critical points in heavy-fermion compounds CeRu2Si2 and YbRh2Si2 using thermoelectric power measurements, highlighting differences in their critical behavior.

Contribution

It provides new thermoelectric power data revealing Lifshitz transitions and compares the quantum criticality in CeRu2Si2 and YbRh2Si2, emphasizing their distinct Fermi surface evolutions.

Findings

Lifshitz transitions are detected near quantum critical points.

Doping CeRu2Si2 with Rh decouples metamagnetic and pseudo-metamagnetic transitions.

Fermi surface is preserved across ferromagnetic and paramagnetic phases in some materials.

Abstract

New thermoelectric power (TEP) measurements on prototype heavy-fermion compounds close to magnetic quantum criticality are presented. The highly sensitive technique of TEP is an unique tool to reveal Fermi surface instabilities, referred here as Lifshitz transitions. The first focus is on the Ising CeRu2Si2 series. Doping CeRu2Si2 with Rh produces a decoupling between the first order metamagnetic transition and the pseudo-metamagnetism observed in the pure compound. Comparison is made with the case of YbRh2Si2 which is often considered as the archetype of local quantum criticality by contrast to CeRu2Si2, taken as an example of spin-density wave criticality. Up to now for ferromagnetic materials showing ferromagnetic wings, no simple case appears where the Fermi surface is preserved between the ferromagnetic and paramagnetic phases. An open issue is the consequence of Lifshitz transitions on superconductivity in these multiband systems.