Quantum Criticality and Population Trapping of Fermions by Non-Equilibrium Lattice Modulations

TL;DR

This paper investigates how periodic lattice modulations in an ultracold fermionic gas induce quantum criticality and enable population trapping, revealing non-equilibrium phase transitions using advanced Green's function techniques.

Contribution

It introduces a non-perturbative Keldysh-Floquet-DMFT approach to study driven Mott insulators, uncovering quantum critical behavior under non-equilibrium conditions.

Findings

Identification of non-equilibrium quantum critical points

Demonstration of population trapping in Floquet states

Transition from Mott insulator to conducting phase

Abstract

An ultracold gas of interacting fermionic atoms in a three-dimensional optical lattice is considered, where the lattice potential strength is periodically modulated. This non-equilibrium system is non-perturbatively described by means of a Keldysh-Floquet-Green's function approach for Mott-Hubbard systems employing a generalized dynamical mean field theory (DMFT). Strong repulsive interactions between different atoms lead to a Mott insulator state for the equilibrium system, but the additional external driving at zero temperature yields a non-equilibrium quantum critical behavior, where an infinite number of Floquet states arise and a transition to the liquid and conducting phase is given.