Competition among various charge-inhomogeneous states and d-wave superconducting state in Hubbard models on square lattices

TL;DR

This paper investigates the competition between charge inhomogeneous states and d-wave superconductivity in Hubbard models, revealing stripe states and phase separation phenomena relevant to cuprate superconductors.

Contribution

It demonstrates how emergent effective attraction from Coulomb repulsion leads to stripe and phase separation states, advancing understanding of competing orders in high-Tc cuprates.

Findings

Stripe states compete energetically with superconductivity.

Stripe period varies with hole doping, matching experimental observations.

Phase separation occurs at low doping levels.

Abstract

We study competitions between charge uniform and inhomogeneous states in two-dimensional Hubbard models by using a variational Monte Carlo method. At realistic parameters for cuprate superconductors, emergent effective attraction of carriers generated from repulsive Coulomb interaction leads to charge/spin stripe ground states, which severely compete with uniform superconducting excited states in the energy scale of 10 K for the cuprates. Stripe period increases with decreasing hole doping $\delta$, which agrees with the experiments for La-based cuprates at $\delta$ = 1/8. For lower $\delta$, we find a phase separation. Implications of the emergent attraction for the cuprates are discussed.