Synthetic Mutual Gauge Field in Microwave-Shielded Polar Molecular Gases

TL;DR

This paper proposes a novel synthetic gauge field in microwave-shielded polar molecular gases, arising from the interplay of microwave shielding and dipolar interactions, which influences the collective motion and breaks time-reversal symmetry.

Contribution

It introduces a mutual gauge field coupling to the relative motion of molecules, a new concept differing from single-particle gauge fields in cold atom systems.

Findings

The gauge field couples to the relative motion of molecules.

It causes breaking of time-reversal symmetry.

The magnetic field distribution resembles a solenoid attached to molecules.

Abstract

The recent breakthrough of realizing the Bose-Einstein condensate of polar molecules and degenerate Fermi molecules in three dimensions relies crucially on the microwave shielding technique, which strongly suppresses the collision loss between molecules. In this letter, we show that the cooperation of microwave shielding and dipolar interaction naturally leads to the emergence of a synthetic gauge field. Unlike that studied in cold atoms before, this gauge field couples to the relative motion of every two molecules instead of single-particle motion, therefore being a mutual gauge field. In this case, every molecule carrying a synthetic charge sees the other molecule as carrying the source of the magnetic field, and the spatial distribution of the magnetic field is reminiscent of a solenoid attached to the molecule. In other words, in addition to microwave-shielded interaction, another part of the interaction between two molecules behaves as a charge interacting with a solenoid, which was missed in the previous discussion. We argue that the physical manifestation of this gauge field is breaking time-reversal symmetry in the collective spatial motion of molecules. Finally, we discuss the challenges in quantitatively studying such a quantum many-body system.