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

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 H_c ∼ 26.5 T, indicating an abrupt reconstruction of the Fermi surface. The electronic band structure was calculated using [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 p_c CeRh₂Si₂ enters in a mixed-valence state. In the PPM state under a high magnetic field, the 4f contribution at the Fermi level E_F drops significantly compared with that in the PM state, and the 4f electrons contribute only weakly to the Fermi surface in our approach.