Enhancement of super-exchange pairing in the periodically-driven Hubbard model

TL;DR

This paper demonstrates that periodic optical driving can enhance electron pairing in strongly-correlated systems like the doped Hubbard model, potentially explaining optically induced superconductivity.

Contribution

It reveals a new mechanism where periodic driving enhances super-exchange interactions and pairing in the Hubbard model, beyond conventional theories.

Findings

Periodic driving reduces electronic hopping while maintaining super-exchange interactions.

Enhanced singlet-pair correlations emerge rapidly in out-of-equilibrium states.

The mechanism may underlie optically induced superconductivity in correlated materials.

Abstract

Recent experiments performed on cuprates and alkali-doped fullerides have demonstated that key signatures of superconductivity can be induced above the equilibrium critical temperature by optical modulation. These observations in disparate physical systems may indicate a general underlying mechanism. Multiple theories have been proposed, but these either consider specific features, such as competing instabilities, or focus on conventional BCS-type superconductivity. Here we show that periodic driving can enhance electron pairing in strongly-correlated systems. Focusing on the strongly-repulsive limit of the doped Hubbard model, we investigate in-gap, spatially inhomogeneous, on-site modulations. We demonstrate that such modulations substantially reduce electronic hopping, while simultaneously sustaining super-exchange interactions and pair hopping via driving-induced virtual charge excitations. We calculate real-time dynamics for the one-dimensional case, starting from zero and finite temperature initial states, and show that enhanced singlet--pair correlations emerge quickly and robustly in the out-of-equilibrium many-body state. Our results reveal a fundamental pairing mechanism that might underpin optically induced superconductivity in some strongly correlated quantum materials.