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

TL;DR

This study investigates the electronic and magnetic phase transitions in Ba2CuO4-, revealing doping-dependent band character changes, magnetic phases, and the evolution of superconducting pairing symmetry with electronic correlation strength.

Contribution

It provides a detailed theoretical analysis of the doping and correlation effects on the electronic structure, magnetic phases, and pairing symmetry in Ba2CuO4-, a recently discovered high-Tc superconductor.

Findings

Doping induces a transition from two-band to single-band character around n=2.5.

Magnetic phases vary with doping and correlation strength, including AFM and paramagnetic states.

Superconducting pairing symmetry crosses over from s-wave to d-wave as U increases beyond 2.2 eV.

Abstract

We present the influences of electronic and magnetic correlations and doping evolution on the groundstate properties of recently discovered superconductor Ba$_{2}$CuO$_{4-\delta}$ by utilizing the Kotliar-Ruckenstein slave boson method. Starting with an effective two-orbital Hubbard model (Scalapino {\it et al.} Phys. Rev. {\bf 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.