Band crossover and magnetic phase diagram of high-Tc superconducting compound Ba2CuO4-δ

Abstract

We present the influences of electronic and magnetic correlations and doping evolution on the groundstate properties of recently discovered superconductor Ba 2 CuO 4−δ by utilizing the Kotliar-Ruckenstein slave boson method. Starting with an effective two-orbital Hubbard model (Scalapino et al. Phys. Rev. B 99, 224515 (2019)), we demonstrate that with increasing doping concentration, the paramagnetic (PM) system evolves from two-band character to single-band ones around the electron filling n=2.5, with the band nature of the d 3z 2 −r 2 and d x 2 −y 2 orbitals to the d x 2 −y 2 orbital, slightly affected when the electronic correlation U varies from 2 to 4 eV. Considering the magnetic correlations, the system displays one antiferromagnetically metallic (AFM) phase in 2 < n < 2.16 and a PM phase in n > 2.16 at U=2 eV, or two AFM phases in 2 < n < 2.57 and 2.76 < n < 3, and a PM phase in 2.57 < n < 2.76 respectively, at U=4 eV. Our results show that near realistic superconducting state around n=2.6 the intermediate correlated Ba 2 CuO 3,2 should be single band character, and the s-wave superconducting pairing strength becomes significant when U>2 eV, and crosses over to d-wave when U>2.2 eV.