Drastic enhancement of d -wave superconductivity in an extended checkerboard Hubbard model

Motivated by the recent discovery of anomalously strong nearest-neighbor attraction in the one-dimensional hole-doped cuprate ${\text{Ba}}_{2+x}{\text{Sr}}_{x}{\text{CuO}}_{3+\ensuremath{\delta}}$, we investigate the $d$-wave superconducting property of an extended checkerboard Hubbard model, which includes an intraplaquette nearest-neighbor attraction $V$. Our quantum Monte Carlo simulations reveal that, for small interplaquette hopping integral ${t}^{\ensuremath{'}}$, $V$ induces a drastic enhancement of long-range $d$-wave pairing correlations in the parameter range of $0.0\ensuremath{\le}U\ensuremath{\le}6.0t$ ($t$ is the intraplaquette hopping integral) when the electron density lies between half-filling and quarter-filling. At $V=\ensuremath{-}0.4t$, one order of magnitude larger $d$-wave pairing correlations are observed compared to the ones at $V=0.0t$ and, more importantly, they exceed the values of the free electron system, signifying the existence of $d$-wave superconductivity. The exact diagonalization calculations on the $2\ifmmode\times\else\texttimes\fi{}2$ plaquette indicate that the enhancement of $d$-wave pairing correlations can be attributed to the $V$-induced enhancement of pair-binding energy. Our findings provide a new perspective on the realization of high-temperature $d$-wave superconductivity via the combination of nearest-neighbor attraction and electronic inhomogeneity.