Pairing phase diagram for electron-doped cuprates in the square-lattice $t-U-V$ Hubbard model

TL;DR

This study explores how nearest-neighbor electron interactions in the $t-U-V$ Hubbard model influence pairing symmetries and density waves, providing insights into the behavior of electron-doped cuprates through quantum Monte Carlo simulations.

Contribution

It demonstrates that NN electron interactions can induce exotic pairing states and modify existing pairing symmetries, offering a minimal model for electron-doped cuprates.

Findings

NN attraction drives $p$-wave spin-triplet pairing

NN repulsion suppresses $d_{x^2-y^2}$-wave pairing and promotes $d_{xy}$-wave pairing

NN repulsion enhances charge density wave and suppresses spin density wave

Abstract

Motivated by significant discrepancies between experimental observations of electron-doped cuprates and numerical results of the Hubbard model, we investigate the role of nearest-neighbor (NN) electron interactions $V$ by studying the $t-U-V$ model on square lattices. Upon doping $\delta$= 0.153, by using constrained path quantum Monte Carlo (CPQMC) method, we find that NN electron attraction $V$ can notably drive an exotic $p$-wave spin-triplet pairing, while the NN electron repulsion $V$ will suppress the $d_{x^2-y^2}$-wave ($d$-wave) pairing and triggers the $d_{xy}$-wave pairing. Especially in the intermediate coupling regime, as NN repulsion increases, the intensity of $d_{xy}$-wave pairing also increases, further suppressing the presence of $d$-wave pairing, which may help explain the notable suppression of $d$-wave pairing in electron-doped cuprate superconductors. Besides the pairing phase, we also find that the NN electron attraction $V$ has no significant effect on spin density wave (SDW) and charge density wave (CDW), but repulsion $V$ significantly enhanced CDW and suppressed SDW. Our study suggests the $t-U-V$ Hubbard model can serve as the minimal model to capture the essential physics of the electron-doped cuprates.