Ground state of the three-band Hubbard model

TL;DR

This study investigates the ground state of the two-dimensional three-band Hubbard model in oxide superconductors using variational Monte Carlo, revealing potential d-wave superconductivity away from half-filling and aligning with experimental phase diagrams.

Contribution

It demonstrates the possible existence of d-wave superconductivity in the three-band Hubbard model away from half-filling, supported by variational Monte Carlo calculations.

Findings

Antiferromagnetic correlations are enhanced near half-filling.

d-wave superconducting state may exist away from half-filling.

Calculated phase diagram qualitatively matches experimental observations.

Abstract

The ground state of the two-dimensional three-band Hubbard model in oxide superconductors is investigated by using the variational Monte Carlo method. The Gutzwiller-projected BCS and spin- density wave (SDW) functions are employed in the search for a possible ground state with respect to dependences on electron density. Antiferromagnetic correlations are considerably enhanced near half-filling. It is shown that the d-wave state may exist away from half-filling for both the hole and electron doping cases. The overall structure of the phase diagram obtained by the calculations qualitatively agrees with experimental indications. The superconducting condensation energy is in reasonable agreement with the experimental value obtained from specific heat and critical magnetic field measurements for optimally doped samples. The inhomogeneous SDW state is also examined near 1/8-hole doping.