Pressure-induced self-doping and Fermi surface reconstruction in UAs2
Superconductivity has recently been reported in the heavy-fermion compound UAs2 under pressure, with the highest Tc among uranium-based correlated 5f-electron superconductors. To elucidate its microscopic origin, we investigate its electronic structure using density functional theory combined with dynamical mean-field theory (DFT+DMFT). At ambient pressure, our calculations reproduce the characteristic Kondo-lattice electronic structure, with flat hybridization bands near the Fermi energy around the Γ and M points, in good agreement with angle-resolved photoemission spectroscopy (ARPES). Under pressure, we find a systematic transfer of electrons from the more localized 5f5/2 orbitals to the more itinerant 5f7/2 orbitals, while the total U-5f occupancy remains nearly unchanged. This orbital-selective charge redistribution constitutes a pressure-induced self-doping effect that drives the 5f5/2 electrons from a localized Kondo regime toward a mixed-valence regime with enhanced charge fluctuations, leading to a dramatic reconstruction of the low-energy electronic structure. Remarkably, superconductivity emerges in the pressure range where the Fermi surface consists of two disconnected sheets with enhanced nesting, but disappears when they bend and merge into a corrugated three-dimensional cylinder. Our results provide an electronic-structure basis for understanding superconductivity in UAs2 and suggest that Fermi-surface nesting and charge fluctuations may contribute to the enhanced superconducting Tc, pointing to a possible distinction from conventional heavy-fermion superconductors.