No Arabic abstract
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-wave 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 dipolar splitting in 6Li p-wave Feshbach resonances by highresolution atom-loss spectroscopy. The Feshbach resonances at 159 G and 215 G exhibit a doublet structure of 10 mG and 13 mG, respectively, associated with different projections of the orbital angular momentum. The observed splittings agree very well with coupled-channel calculations. We map out the temperature dependence of the atom-loss spectrum allowing us to extrapolate resonance positions and the corresponding widths to zero temperature. The observed dipolar splitting in fermionic lithium might be useful for the realization of the quantum phase transition between the polar and axial p-wave superfluid phases.
We present an exactly-solvable $p$-wave pairing model for two bosonic species. The model is solvable in any spatial dimension and shares some commonalities with the $p + ip$ Richardson-Gaudin fermionic model, such as a third order quantum phase transition. However, contrary to the fermionic case, in the bosonic model the transition separates a gapless fragmented singlet pair condensate from a pair Bose superfluid, and the exact eigenstate at the quantum critical point is a pair condensate analogous to the fermionic Moore-Read state.
We show that recently suggested subwavelength lattices offer remarkable prospects for the observation of novel superfluids of fermionic polar molecules. It becomes realistic to obtain a topological $p$-wave superfluid of microwave-dressed polar molecules in 2D lattices at temperatures of the order of tens of nanokelvins, which is promising for topologically protected quantum information processing. Another foreseen novel phase is an interlayer $p$-wave superfluid of polar molecules in a bilayer geometry.
We report the observation of three p-wave Feshbach resonances of $^6$Li atoms in the lowest hyperfine state $f=1/2$. The positions 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, 2- or 3-body mechanisms are at play. In the case of dipolar losses, we observe a non-trivial temperature dependence that is well explained by a simple model.
We study a continuum model of the weakly interacting Bose gas in the presence of an external field with minima forming a triangular lattice. The second lowest band of the single-particle spectrum ($p$-band) has three minima at non-zero momenta. We consider a metastable Bose condensate at these momenta and find that, in the presence of interactions that vary slowly over the lattice spacing, the order parameter space is isomorphic to $S^{5}$. We show that the enlarged symmetry leads to the loss of topologically stable vortices, as well as two extra gapless modes with quadratic dispersion. The former feature implies that this non-Abelian condensate is a failed superfluid that does not undergo a Berezinskii-Kosterlitz-Thouless (BKT) transition. Order-by-disorder splitting appears suppressed, implying that signatures of the $S^5$ manifold ought to be observable at low temperatures.