Observation of Broad d-Wave Feshbach Resonances with a Triplet Structure

High partial-wave (l >= 2) Feshbach resonance (FR) in an ultracold mixture of Rb-85-Rb-87 atoms is investigated experimentally aided by a partial-wave insensitive analytic multichannel quantum-defect theory. Two broad resonances from coupling between d waves in both the open and closed channels are observed and characterized. One of them shows a fully resolved triplet structure with a splitting ratio well explained by the perturbation to the closed channel due to interatomic spin-spin interaction. These tunable broad d-wave resonances, especially the one in the lowest-energy open channel, could find important applications in simulating d-wave coupling dominated many-body systems. In addition, we find that there is generally a time and temperature requirement, associated with tunneling through the angular momentum barrier, to establish and observe resonant coupling in nonzero partial waves.