# Fermi Surfaces in the Antiferromagnetic, Paramagnetic and Polarized Paramagnetic States of CeRh2Si2 Compared with Quantum Oscillation Experiments

## TL;DR

This study investigates the Fermi surface reconstructions in CeRh2Si2 across different magnetic states using band structure calculations and compares them with quantum oscillation experiments, revealing abrupt changes at the transition.

## Contribution

It provides a detailed comparison of LDA+U and LDA calculations with experimental data, highlighting the Fermi surface evolution in different magnetic states of CeRh2Si2.

## Key findings

- Fermi surface undergoes an abrupt reconstruction at the transition to the polarized paramagnetic state.
- LDA calculations better match experimental data, suggesting a mixed-valence state above critical pressure.
- 4f electron contribution at the Fermi level decreases significantly in the high-field PPM state.

## Abstract

The large quantum oscillations observed in the thermoelectric power in the antiferromagnetic (AF) state of the heavy-fermion compound CeRh2Si2 disappear suddenly when entering in the polarized paramagnetic (PPM) state at Hc=26.5 T, indicating an abrupt reconstruction of the Fermi surface. The electronic band structure was [LDA+U] for the AF state taking the correct magnetic structure into account, for the PPM state, and for the paramagnetic state (PM). Different Fermi surfaces were obtained for the AF, PM, and PPM states. Due to band folding, a large number of branches was expected and observed in the AF state. The LDA+U calculation was compared with the previous LDA calculations. Furthermore, we compared both calculations with previously published de Haas-van Alphen experiments. The better agreement with the LDA approach suggests that above the critical pressure pc CeRh2Si2 enters in a mixed-valence state. In the PPM state under a high magnetic field, the 4f contribution at the Fermi level EF drops significantly compared with that in the PM state, and the 4f electrons contribute only weakly to the Fermi surface in our approach.