Fermi surface instabilities in CeRh2Si2 at high magnetic field and pressure

TL;DR

This study investigates Fermi surface changes in CeRh2Si2 under high magnetic field and pressure, revealing significant electronic structure reconstructions linked to magnetic and valence fluctuations.

Contribution

It provides new insights into Fermi surface instabilities and their relation to magnetic and valence fluctuations in CeRh2Si2 under extreme conditions.

Findings

Quantum oscillations in TEP vanish at the PPM transition.

S/T increases near the critical pressure, indicating FS change.

Band calculations show different 4f contributions in AF and PM phases.

Abstract

We present thermoelectric power (TEP) studies under pressure and high magnetic field in the antiferromagnet CeRh2Si2 at low temperature. Under magnetic field, large quantum oscillations are observed in the TEP, S(H), in the antiferromagnetic phase. They suddenly disappear when entering in the polarized paramagnetic (PPM) state at Hc pointing out an important reconstruction of the Fermi surface (FS). Under pressure, S/T increases strongly of at low temperature near the critical pressure Pc, where the AF order is suppressed, implying the interplay of a FS change and low energy excitations driven by spin and valence fluctuations. The difference between the TEP signal in the PPM state above Hc and in the paramagnetic state (PM) above Pc can be explained by different FS. Band structure calculations at P = 0 stress that in the AF phase the 4f contribution at the Fermi level (EF) is weak while it is the main contribution in the PM domain. By analogy to previous work on CeRu2Si2, in the PPM phase of CeRh2Si2 the 4f contribution at EF will drop.