Origin of high-Tc superconductivity in doped Hubbard models and their extensions: Roles of uniform charge fluctuations

TL;DR

This study uses advanced variational Monte Carlo methods to explore the doped Hubbard model, revealing that high-Tc superconductivity is closely linked to charge fluctuations and phase separation, influenced by intersite Coulomb and superexchange interactions.

Contribution

It provides new insights into the origin of high-Tc superconductivity, emphasizing the roles of charge fluctuations and phase separation in doped Hubbard models.

Findings

Superconductivity emerges near phase separation regions.

Charge compressibility enhancement correlates with superconducting order.

Interplay of Coulomb and superexchange interactions affects phase stability.

Abstract

Doped Hubbard model is a simple model for the high-Tc cuprate superconductors, while its ground state remains a challenge. Here, by performing state-of-the-art variational Monte Carlo calculations for the strong-coupling Hubbard model, we find evidences that the d-wave superconducting phase emerges always near the phase separation region and the superconducting order has one-to-one correspondence with the enhancement of charge compressibility. The order as well as the phase separation are vulnerable to realistic intersite Coulomb interaction while the superexchange interaction enhances both. An appropriate combination of these two widens the stable superconducting phase.