Optical control of a magnetic Feshbach resonance in ultracold Fermi gases

TL;DR

This paper demonstrates optical control of magnetic Feshbach resonances in ultracold $^{40}$K gases using near-resonant laser light, enabling precise manipulation of interatomic interactions with minimal atomic loss.

Contribution

It introduces a method to control Feshbach resonances via laser coupling to excited molecular states, expanding the toolkit for tuning interactions in ultracold gases.

Findings

Nine bound-to-bound resonances observed below the molecular threshold.

Laser-dressed bound states characterized by RF spectroscopy.

Magnetic Feshbach resonance shifted with negligible atomic loss.

Abstract

We use laser light near-resonant with a molecular bound-to-bound transition to control a magnetic Feshbach resonance in ultracold Fermi gases of $^{40}$K atoms. The spectrum of excited molecular states is measured by applying a laser field that couples the ground Feshbach molecular state to electronically excited molecular states. Nine strong bound-to-bound resonances are observed below the $^{2}P_{1/2}+^{2}S_{1/2}$ threshold. We use radio-frequency spectroscopy to characterize the laser-dressed bound state near a specific bound-to-bound resonance and show clearly the shift of the magnetic Feshbach resonance using light with negligible atomic loss. The demonstrated technology could be used to modify interatomic interactions with high spatial and temporal resolutions in the crossover regime from a Bose-Einstein condensate (BEC) to a Bardeen-Cooper-Schrieffer (BCS) superfluid.