Understanding superfluidity with higher order partial waves is crucial for the understanding of high-$T_c$ superconductivity. For the realization of a superfluid with anisotropic order parameter, spin-polarized fermionic lithium atoms with strong p-w
ave interaction are the most promising candidates to date. We apply rf-spectroscopy techniques that do not suffer from severe final-state effects cite{Perali08} with the goal to perform photoemission spectroscopy on a strongly interacting p-wave Fermi gas similar to that recently applied for s-wave interactions cite{Stewart08}. Radiofrequency spectra of both quasibound p-wave molecules and free atoms in the vicinity of the p-wave Feshbach resonance located at 159.15,G cite{Schunck05} are presented. The observed relative tunings of the molecular and atomic signals in the spectra with magnetic field confirm earlier measurements realized with direct rf-association cite{Fuchs08}. Furthermore, evidence of bound molecule production using adiabatic ramps is shown. A scheme to observe anisotropic superfluid gaps, the most direct proof of p-wave superfluidity, with 1d-optical lattices is proposed.
We report on the observation of five Feshbach resonances in collisions between ultracold $^7$Li and $^{87}$Rb atoms in the absolute ground state mixture where both species are in their $|f,m_f>=|1,1>$ hyperfine states. The resonances appear as trap l
osses for the $^7$Li cloud induced by inelastic heteronuclear three-body collisions. The magnetic field values where they occur are important quantities for an accurate determination of the interspecies interaction potentials. Results of coupled channels calculations based on the observed resonances are presented and refined potential parameters are given. A very broad Feshbach resonance centered around 649 G should allow for fine tuning of the interaction strength in future experiments.
We report on the first observation of Bragg scattering of an ultracold $^6$Li Fermi gas. We demonstrate a Ramsey-type matter-wave interferometer based on Bragg diffraction and find robust signatures of persistent matter wave coherences using an echo
pulse sequence. Because of the Pauli principle, the diffracted fermions oscillate nearly unperturbed in the trapping potential for long times beyond 2 s. This suggests extremely long coherence times. On these timescales, only the presence of a $^{87}$Rb cloud seems sufficient to induce noticeable perturbations.
We report on measurements of cross-species thermalization inside a magnetically trapped spin-polarized mixture of $^{87}$Rb and $^7$Li atoms with both atoms in their respective low field seeking magnetic substates $|F=2,m_F=2right>$. Measurement of t
he thermalization velocity in the ultracold regime below $10 mu$K allows for the derivation of the absolute value of the pure triplet s-wave scattering length governing the interaction. We find $|a_{7,87}|=(59pm19) a_{rm B}$. We propose to study both species in the condensed regime to derive the sign of $a_{7,87}$. In this context, we present numerical solutions to the coupled Gross-Pitaevskii equation based on the hypothesis of a positive sign. According to the simulations, phase separation of the Li and Rb $|2,2right>$ clouds occurs along with a mean-field stabilization allowing for larger atom numbers of condensed $^7$Li atoms before collapse sets in. Observation of this mean-field stabilization would directly fix the sign of $a_{7,87}$. We discuss our results in the light of this proposal.
