Antagonistic effects of nearest-neighbor repulsion on the superconducting pairing dynamics in the doped Mott insulator regime

TL;DR

This study investigates how nearest-neighbor Coulomb repulsion influences d-wave superconductivity in doped Mott insulators, revealing complex effects on transition temperature and pairing mechanisms through advanced computational methods.

Contribution

It provides a detailed dynamical analysis showing that low-frequency pairing contributions can counteract high-frequency depairing effects of Coulomb repulsion, highlighting the importance of retardation in pairing.

Findings

V increases Tc in the underdoped regime but decreases it in the overdoped regime.

Low-frequency pairing contributions can reinforce superexchange despite Coulomb repulsion.

Retardation effects are crucial for understanding pairing in doped Mott insulators.

Abstract

The nearest-neighbor superexchange-mediated mechanism for d_{x^2-y^2}-wave superconductivity in the one-band Hubbard model faces the challenge that nearest-neighbor Coulomb repulsion can be larger than superexchange. To answer this question, we use cellular dynamical mean-field theory (CDMFT) with a continuous-time quantum Monte Carlo solver to determine the superconducting phase diagram as a function of temperature and doping for on-site repulsion $U=9t$ and nearest-neighbor repulsion $V=0,2t,4t$. In the underdoped regime, $V$ increases the CDMFT superconducting transition temperature $T_c^d$ even though it decreases the superconducting order parameter at low temperature for all dopings. However, $V$ decreases $T_c^d$ in the overdoped regime. We gain insight into these paradoxical results through a detailed study of the frequency dependence of the anomalous spectral function, extracted at finite temperature via the MaxEntAux method for analytic continuation. A systematic study of dynamical positive and negative contributions to pairing reveals that even though $V$ has a high-frequency depairing contribution, it also has a low frequency pairing contribution since it can reinforce superexchange through $J=4t^2/(U-V)$. Retardation is thus crucial to understand pairing in doped Mott insulators, as suggested by previous zero-temperature studies. We also comment on the tendency to charge order for large $V$ and on the persistence of d-wave superconductivity over extended-$s$ or s+d-wave.