Population trapping and inversion in ultracold Fermi gases by excitation of the optical lattice - Non-equilibrium Floquet-Keldysh description

TL;DR

This paper investigates how ultracold Fermi gases in an optical lattice can exhibit population trapping and inversion when externally modulated, using a non-equilibrium Floquet-Keldysh framework to reveal modified band structures.

Contribution

It introduces a non-equilibrium dynamical mean field theory approach to analyze Floquet band structures and population dynamics in ultracold Fermi gases under lattice modulation.

Findings

Identification of Floquet-fan like bandstructure effects

Observation of non-equilibrium population trapping and inversion

Demonstration of dynamical Franz-Keldysh splitting

Abstract

A gas of ultracold interacting quantum degenerate Fermions is considered in a three dimensional optical lattice which is externally modulated in the fre- quency and the amplitude. This theoretical study utilizes the Keldysh formalism to account for the system being out of thermodynamical equilibrium. A dynamical mean field theory, extended to non-equilibrium, is presented to calculate characteristic quantities such as the local density of states and the non-equilibrium distribution function. A dynamics Franz-Keldysh splitting is found which accounts for the non-equilibrium modification of the underlying bandstructure. The found characteristic Floquet-fan like bandstructure accounts for the quantized nature of the effect over all frequency space.