Dynamical band flipping in fermionic lattice systems: An ac-field-driven change of the interaction from repulsive to attractive

TL;DR

This paper demonstrates theoretically that applying an ac field to correlated lattice fermions can invert the band structure and switch the interaction from repulsive to attractive, enabling potential superconductivity.

Contribution

It introduces a novel method to dynamically flip the interaction sign in fermionic systems using ac fields, supported by numerical simulations.

Findings

Interaction can be switched from repulsive to attractive with ac fields.

System reaches a negative temperature with population inversion.

Proposed ramp-up protocol suppresses heating, enabling superconductivity.

Abstract

We show theoretically that the sudden application of an appropriate ac field to correlated lattice fermions flips the band structure and effectively switches the interaction from repulsive to attractive. The nonadiabatically driven system is characterized by a negative temperature with a population inversion. We numerically demonstrate the converted interaction in an ac-driven Hubbard model with the nonequilibrium dynamical mean-field theory solved by the continuous-time quantum Monte Carlo method. Based on this, we propose an efficient ramp-up protocol for ac fields that can suppress heating, which leads to an effectively attractive Hubbard model with a temperature below the superconducting transition temperature of the equilibrium system.