Reshaped three-body interactions and the observation of an Efimov state in the continuum.

Efimov trimers are exotic three-body quantum states that emerge from the different types of three-body continua in the vicinity of two-atom Feshbach resonances. In particular, as the strength of the interaction is decreased to a critical point, an Efimov state merges into the atom-dimer threshold and eventually dissociates into an unbound atom-dimer pair. Here we explore the Efimov state in the vicinity of this critical point using coherent few-body spectroscopy in Li atoms using a narrow two-body Feshbach resonance.

Spin-Conservation Propensity Rule for Three-Body Recombination of Ultracold Rb Atoms.

We explore the physical origin and the general validity of a propensity rule for the conservation of the hyperfine spin state in three-body recombination. This rule was recently discovered for the special case of ^{87}Rb with its nearly equal singlet and triplet scattering lengths. Here, we test the propensity rule for ^{85}Rb for which the scattering properties are very different from ^{87}Rb.

Observation of Efimov Universality across a Nonuniversal Feshbach Resonance in ^{39}K.

We study three-atom inelastic scattering in ultracold ^{39}K near a Feshbach resonance of intermediate coupling strength. The nonuniversal character of such resonance leads to an abnormally large Efimov absolute length scale and a relatively small effective range r_{e}, allowing the features of the ^{39}K Efimov spectrum to be better isolated from the short-range physics. Meticulous characterization of and correction for finite-temperature effects ensure high accuracy on the measurements of these features at large-magnitude scattering lengths.

Precision Test of the Limits to Universality in Few-Body Physics.

We perform precise studies of two- and three-body interactions near an intermediate-strength Feshbach resonance in ^{39}K at 33.5820(14) G. Precise measurement of dimer binding energies, spanning three orders of magnitude, enables the construction of a complete two-body coupled-channel model for determination of the scattering lengths with an unprecedented low uncertainty.