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Register a new userSpin-rotation coupling in p-wave Feshbach resonances
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We report evidence for spin-rotation coupling in $p$-wave Feshbach resonances in an ultracold mixture of fermionic $^6$Li and bosonic $^{133}$Cs lifting the commonly observed degeneracy of states with equal absolute value of orbital-angular-momentum projection on the external magnetic field. By employing magnetic field dependent atom-loss spectroscopy we find triplet structures in $p$-wave resonances. Comparison with coupled-channel calculations, including contributions from both spin-spin and spin-rotation interactions, yields a spin-rotation coupling parameter $|gamma|=0.566(50)times10^{-3}$. Our findings highlight the potential of Feshbach resonances in revealing subtle molecular couplings and providing precise information on electronic and nuclear wavefunctions, especially at short internuclear distance. The existence of a non-negligible spin-rotation splitting may have consequences for future classifications of $p$-wave superfluid phases in spin-polarized fermions.
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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 measure higher partial wave Feshbach resonances in an ultracold mixture of fermionic $^6$Li and bosonic $^{133}$Cs by magnetic field dependent atom-loss spectroscopy. For the $p$-wave Feshbach resonances we observe triplet structures corresponding to different projections of the pair rotation angular momentum onto the external magnetic field axis. We attribute the splittings to the spin-spin and spin-rotation couplings by modelling the observation using a full coupled-channel calculation. Comparison with an oversimplified model, estimating the spin-rotation coupling by describing the weakly bound close-channel molecular state with the perturbative multipole expansion, reveals the significant contribution of the molecular wavefunction at short internuclear distances. Our findings highlight the potential of Feshbach resonances in providing precise information on short- and intermediate-range molecular couplings and wavefunctions. The observed $d$-wave Feshbach resonances allow us to refine the LiCs singlet and triplet ground-state molecular potential curves at large internuclear separations.
We report on the observation of weakly-bound dimers of bosonic Dysprosium with a strong universal s-wave halo character, associated with broad magnetic Feshbach resonances. These states surprisingly decouple from the chaotic backgound of narrow resonances, persisting across many such narrow resonances. In addition they show the highest reported magnetic moment $musimeq20,mu_{rm B}$ of any ultracold molecule. We analyze our findings using a coupled-channel theory taking into account the short range van der Waals interaction and a correction due to the strong dipole moment of Dysprosium. We are able to extract the scattering length as a function of magnetic field associated with these resonances and obtain a background scattering length $a_{rm bg}=91(16),a_0$. These results offer prospects of a tunability of the interactions in Dysprosium, which we illustrate by observing the saturation of three-body losses.
Helium atoms in the metastable $2^3{S_{1}}$ state (He$^*$) have unique advantages for ultracold atomic experiments. However, there is no known accessible Feshbach resonance in He$^*$, which could be used to manipulate the scattering length and hence unlock several new experimental possiblities. Previous experimental and theoretical studies for He$^*$ have produced contradictory results. We aimed to resolve this discrepancy with a theoretical search for Feshbach resonances, using a new close-coupled model of He$^*$ collisions in the presence of an external magnetic field. Several resonances were detected and the existing literature discrepancy was resolved. Although none of the resonances identified are readily experimentally useable, an interesting non-Feshbach scattering length variation with magnetic field was observed in heteronuclear collisions, at field strengths that are experimentally accessible.
We measure the binding energies of weakly bound Feshbach molecules formed between Na and Rb atoms in their lowest hyperfine Zeeman levels. We form molecules at the Feshbach resonance near 347.64 G and dissociate them by magnetic field modulation. We use the binding energies to refine the singlet and triplet potential energy curves, using coupled-channel bound-state calculations. We then use coupled-channel scattering calculations on the resulting potentials to produce a high-precision mapping between magnetic field and scattering length. We also observe 10 additional $s$-wave Feshbach resonances for Na and Rb in different combinations of Zeeman sublevels of the $F = 1$ hyperfine states. Some of the resonances show 2-body inelastic decay due to spin exchange. We compare the resonance properties with coupled-channel scattering calculations that full take account of inelastic properties.
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