P-wave Feshbach resonances of ultracold ⁶Li

We report the observation of three p-wave Feshbach resonances of 6 Li atoms in the lowest hyperfine state f =1/2. Thepositions of the resonances are in good agreement with theory. We study the lifetime of the cloud in the vicinity of the Feshbach resonances and show that, depending on the spin states, two- or three-body mechanisms are at play. In the case of dipolar losses, we observe a nontrivial temperature dependence that is well explained by a simple model. DOI: 10.1103/PhysRevA.70.030702 In the presence of a magnetic field, it is possible to obtain a quasidegeneracy between the relative energy of two colliding atoms and that of a weakly bound molecular state. This effect, known as a Feshbach resonance, is usually associated with the divergence of the scattering length and is the key ingredient that led to the recent observation of superfluids from fermion atom pairs of 6 Li [1‐4] and 40 K [5] .U p to now these pairs were formed in s-wave channels but it is known from condensed matter physics that fermionic superfluidity can arise through higher angular momentum pairing: p-wave Cooper pairs have been observed in 3 He [6] and d-wave cooper pairs in high-Tc superconductivity [7]. Although Feshbach resonances involving p or higher partial waves have been found in cold atom systems [8‐10], p-wave atom pairs have never been directly observed. In this paper we report the observation of three narrow p-wave Feshbach resonances of 6 Li in the lowest hyperfine state f =1/2. We measure the position of the resonance as well as the lifetime of the atomic sample for all combinations uf =1/2, mfl + uf =1/2, m fl, henceforth denoted smf , m fd .W e show that the position of the resonances are in good agreement with theory. In the case of atoms polarized in the ground state s 1/2,1/2 d, the atom losses are due to threebody processes. We show that the temperature dependence of the losses at resonance cannot be described by the threshold law predicted by [11] on the basis of the symmetrization principle for identical particles. In the case of atoms polarized in s ˛1/2,˛1/2 d or that of a mixture s 1/2,˛1/2 d, the losses are mainly due to two-body dipolar losses. These losses show a nontrivial temperature dependence that can nevertheless be understood by a simple theoretical model with only one adjustable parameter. In the s 1/2,˛1/2 d channel, we take advantage of a sharp decrease of the two-body loss rate below the Feshbach resonance to present a first evidence for the generation of p-wave molecules.