Observation of Universality in Ultracold ${}^7\mathrm{Li}$ Three-Body Recombination

We report on experimental evidence of universality in ultracold ${}^7\mathrm{Li}$ atoms’ three-body recombination loss in the vicinity of a Feshbach resonance. We observe a recombination minimum and an Efimov resonance in regions of positive and negative scattering lengths, respectively, which are connected through the pole of the Feshbach resonance. Both observed features lie deeply within the range of validity of the universal theory, and we find that the relations between their properties, i.e., widths and locations, are in excellent agreement with the theoretical predictions.

Figure 1

The scattering length $a$ (solid line) and the effective range $R_e$ (dashed line) as a function of magnetic field near the two Feshbach resonances of the $|F=1,m_F=0⟩$ state.

Figure 2

Three-body loss coefficient $K_3$ is shown as a function of magnetic field and scattering length (insets). The solid lines represent fittings to the analytical expressions of universal theory. The dashed lines represent the upper (lower) limit of $K_3$ for $a>0$ ($a<0$). The error bars consist of two contributions: the uncertainty in temperature measurement ($\sim 20\%$) which affects the estimated atom density and the fitting error of the lifetime measurement.