Enhanced pairing susceptibility in a photo-doped two-orbital Hubbard model

TL;DR

This paper demonstrates that photo-doping in a two-orbital Hubbard model can significantly enhance pairing susceptibility in the large-U regime by creating charge states that promote local spin fluctuations, as shown through nonequilibrium simulations.

Contribution

It introduces a method to boost pairing susceptibility in strongly correlated systems via photo-doping, revealing a link between charge state populations and pairing enhancement.

Findings

Photo-doping increases pairing susceptibility at large U.

Enhanced pairing correlates with local spin susceptibility.

Ultra-fast cooling of carriers supports pairing enhancement.

Abstract

Local spin fluctuations provide the glue for orbital-singlet spin-triplet pairing in the doped Mott insulating regime of multi-orbital Hubbard models. At large Hubbard repulsion $U$, the pairing susceptibility is nevertheless very low, because the pairing interaction cannot overcome the suppression of charge fluctuations. Using nonequilibrium dynamical mean field simulations of the two-orbital Hubbard model, we show that out of equilibrium the pairing susceptibility in this large-$U$ regime can be strongly enhanced by creating a photo-induced population of the relevant charge states, and that this susceptibility correlates with the local spin susceptibility. Since a strong enhancement of the pairing requires a low kinetic energy of the charge carriers, the phenomenon is supported by the ultra-fast cooling of the photo-doped carriers through the creation of local spin excitations.