Five- and Six-Body Resonances Tied to an Efimov Trimer

Evidence for universal four-body states tied to an Efimov trimer.

We report on the measurement of four-body recombination rate coefficients in an atomic gas. Our results obtained with an ultracold sample of cesium atoms at negative scattering lengths show a resonant enhancement of losses and provide strong evidence for the existence of a pair of four-body states, which is strictly connected to Efimov trimers via universal relations. Our findings confirm recen...

Single-Particle Momentum Distribution of an Efimov trimer

Observation of heteronuclear atomic Efimov resonances.

Building on the recent experimental observation with ultracold atoms, we report the first experimental evidence of Efimov physics in a heteronuclear system. A mixture of ;{41}K and ;{87}Rb atoms was cooled to few hundred nanokelvins and stored in an optical dipole trap. Exploiting a broad interspecies Feshbach resonance, the losses due to three-body collisions were studied as a function of the ...

Test of the universality of the three-body Efimov parameter at narrow Feshbach resonances.

We measure the critical scattering length for the appearance of the first three-body bound state, or Efimov three-body parameter, at seven different Feshbach resonances in ultracold ^{39}K atoms. We study both intermediate and narrow resonances, where the three-body spectrum is expected to be determined by the nonuniversal coupling of two scattering channels. Instead, our observed ratio of the ...

Efimov states with strong three-body losses

Introduction. – Motivated by nuclear physics, Efimov discovered that three particles with short-ranged two-body interactions of scattering length |a| = ∞ can support an infinite series of weakly bound trimer states [1]. In contrast to systems of nucleons or of He atoms, ultracold gases of alkali metal atoms offer the possibility to tune a by using a Feshbach resonance, and thus to go more deepl...