$GW$+EDMFT investigation of Pr$_{1-x}$Sr$_x$NiO$_2$ under pressure

Abstract

Motivated by the recent experimental observation of a large pressure effect on $T_c$ in Pr$_{1-x}$Sr$_x$NiO$_2$, we study the electronic properties of this compound as a function of pressure for $x=0$ and $0.2$ doping using self-consistent $GW$+EDMFT. Our numerical results demonstrate a non-trivial interplay between chemical doping and physical pressure, and small but systematic changes in the orbital occupations, local level energies, and interaction parameters with increasing pressure. The proper treatment of correlation effects, beyond density function theory, is shown to play an important role in revealing these trends. While the pressure dependent changes in the electronic structure of the undoped compound suggest a more single-band-like behavior in the high-pressure regime, a qualitatively different behavior is found in the doped system. We also point out that the fluctuations in the orbital occupations and spin states are not consistent with a single-band picture, and that at least a two-band model is necessary to reproduce the full result. This multi-orbital nature manifests itself most clearly in the doped compound.