High-magnetic-fields thermodynamics of the heavy-fermion metal YbRh

We perform a comprehensive theoretical analysis of the high-magnetic-field behavior of the heavy-fermion (HF) compound YbRh2Si2. At low magnetic fields B, YbRh2Si2 has a quantum critical point related to the suppression of antiferromagnetic ordering at a critical magnetic field B⊥c of B = Bc0 ≃ 0.06 T. Our calculations of the thermodynamic properties of YbRh2Si2 in wide magnetic field range from Bc0 ≃ 0.06 T to B ≃ 18 T allow us to straddle a possible metamagnetic transition region and probe the properties of both low-field HF liquid and high-field fully polarized one. Namely, high magnetic fields B∼B*∼10 T fully polarize the corresponding quasiparticle band generating a Landau-Fermi-liquid (LFL) state and suppressing the HF (actually NFL) one, while at increasing temperatures both the HF state and the corresponding NFL properties are restored. Our calculations are in good agreement with experimental facts and show that the fermion condensation quantum phase transition is indeed responsible for the observed NFL behavior and quasiparticles survive both high temperatures and high magnetic fields