Artificial electromagnetic field with cold atoms in two-dimensional optical lattice

TL;DR

This paper demonstrates how to engineer an artificial electromagnetic field in a cold atom system within a 2D optical lattice, revealing quantum Hall effects, dynamical phase transitions, and superradiance through cavity coupling.

Contribution

It introduces a novel method to create and study artificial electromagnetic fields in cold atom systems using cavity QED and two-photon processes, highlighting non-equilibrium dynamics.

Findings

Reveals Hofstadter butterfly spectrum in the bulk

Shows emergence of quantum Hall edge modes

Identifies dynamical phase transitions driven by magnetic flux

Abstract

We propose that an artificial electromagnetic field can be engineered in the context of cold fermionic atoms that are coupled to a cavity mode via two-photon processes in a two-dimensional optical lattice. There is a standing-wave pump laser inducing the electric effect in one spatial direction, and a second running-wave laser beam generates the magnetic flux perpendicular to the lattice plane. In the static scenario, the bulk spectrum resembles the fractal structure of the Hofstadter butterfly and the edge mode spectrum indicates the occurrence of the quantum Hall phase. The Keldysh formulism is utilized to capture the time evolution. The back action between atoms and cavity field gives a picture of the time-dependent non-equilibrium dynamics. We find that the spontaneous emergence of the artificial electromagnetic field stimulates the Hall current, and the superradiant cavity field emerges without pump threshold. Moreover, the magnetic flux not only modify the bulk topology, but also drives a series of dynamical phase transitions.