arXiv subjects

C. Welford

Publications and source records attributed to C. Welford.

2 recordsLinked to original sources

arXiv2008

Photoassociation of a Bose-Einstein Condensate near a Feshbach Resonance

We measure the effect of a magnetic Feshbach resonance (FR) on the rate and light-induced frequency shift of a photoassociation resonance in ultracold $^7$Li. The photoassociation-induced loss rate coefficient, $K_p$, depends strongly on magnetic field, varying by more than a factor of 10$^4$ for fields near the FR. At sufficiently high laser intensities, $K_p$ for a thermal gas decreases with increasing intensity, while saturation is observed for the first time in a Bose-Einstein condensate. The frequency shift is also strongly field-dependent and exhibits an anomalous blue-shift for fields just below the FR.

cond-mat.other↗

arXiv2008

Phase Coherence and Superfluid-Insulator Transition in a Disordered Bose-Einstein Condensate

We have studied the effects of a disordered optical potential on the transport and phase coherence of a Bose-Einstein condensate (BEC) of 7Li atoms. At moderate disorder strengths (V_D), we observe inhibited transport and damping of dipole excitations, while in time-of-flight images, random but reproducible interference patterns are observed. In-situ images reveal that the appearance of interference is correlated with density modulation, without complete fragmentation. At higher V_D, the interference contrast diminishes as the BEC fragments into multiple pieces with little phase coherence.

cond-mat.other↗