Stripe order enhanced superconductivity in the Hubbard model

TL;DR

This study shows that stripe order, modeled as periodic modulation in the Hubbard model, can significantly enhance superconductivity and induce a phase with a spin gap and quasi-long-range order.

Contribution

It demonstrates through DMRG simulations that stripe-like modulations can promote superconductivity in the Hubbard model, suggesting a positive role of inhomogeneities in high-temperature superconductivity.

Findings

Stripe order modulations enhance superconducting correlations by many orders of magnitude.

Modulations induce a phase with a substantial spin gap and quasi-long-range superconducting order.

Superconducting correlations are characterized by a Luttinger exponent around 1.

Abstract

Unidirectional ("stripe") charge-density-wave order has now been established as a ubiquitous feature in the phase diagram of the cuprate high temperature (HT) superconductors, where it generally competes with superconductivity (SC). None-the-less, on theoretical grounds it has been conjectured that stripe order (or other forms of "optimal" inhomogeneities) may play an essential positive role in the mechanism of HTSC. Here we report density matrix renormalization group studies of the Hubbard model on long 4 and 6 leg cylinders where the hopping matrix elements transverse to the long direction are periodically modulated - mimicing the effect of putative period-2 stripe order. We find even modest amplitude modulations can enhance the long-distance SC correlations by many orders of magnitude, and drive the system into a phase with a substantial spin gap and SC quasi-long-range-order with a Luttinger exponent, $K_{sc} \sim 1$.