Optical control of the scattering length and effective range for magnetically tunable Feshbach resonances in ultracold gases

摘要

We describe two-field optical techniques to control interactions in Feshbach resonances for two-body scatteringnin ultracold gases. These techniques create a molecular dark state in the closed channel of a magneticallyntunable Feshbach resonance, greatly suppressing optical scattering compared to single optical field methods.nThe dark-state method enables control of the effective range, by creating narrow features that modify the energyndependence of the scattering phase shift, as well as control of the elastic and inelastic parts of the zero-energyns-wave scattering amplitude. We determine the scattering length and the effective range from an effective rangenexpansion, by calculating the momentum-dependent scattering phase shift from the two-body scattering state.