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

We present the influences of electronic and magnetic correlations and doping on the ground-state properties of the recently discovered superconductor Ba2CuO4-delta by utilizing the rotationally invariant 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 a two-band character to single band around the electron filling n = 2.5, with the band nature of the d(3z2-r2) and d(x2-y2) orbitals to the d(3z2-r2) orbital, slightly affected when the electronic correlation U varies from 2 to 4 eV. Considering the magnetic correlations, the system displays one antiferromagnetic (AFM) metallic phase in 2 < n < 2.14 and a PM phase in n > 2.14 at U = 2 eV, or two AFM metallic phases in 2 < n < 2.52 and 2.74 < n < 3, and a PM phase in 2.52 < n < 2.74, respectively, at U = 4 eV. Our results show that near the realistic superconducting state around n = 2.6 the intermediate correlated Ba2CuO3,2 should be of single-band character. The s-wave superconducting pairing strength becomes significant when U > 2 eV, and crosses over to d wave when U > 2.2 eV.