Feshbach resonances in fermionicLi6

Abstract

Feshbach resonances in 6 Li were experimentally studied and theoretically analyzed. In addition to two previously known s-wave resonances, we found three p-wave resonances. Four of these resonances are narrow and yield a precise value of the singlet scattering length, but do not allow us to accurately predict the location of the broad resonance near 83 mT. Its position was previously measured in a molecule-dissociation experiment for which we, here, discuss systematic shifts. [2,4,6,7,8,9,10].In 6 Li these experiments have been carried out in the vicinity of the s-wave Feshbach resonance near 830 G [2,4,7,8,9,10] (1 G = 10 −4 Tesla). The quantitative interpretation of these experiments and the characterization of the BEC-BCS crossover require a precise knowledge of the resonance location. However, its determination is not trivial since the resonance width is extremely large (180 G), and the line shape is strongly affected by many body effects. In our previous work we determined the position of this resonance by the onset of molecule dissociation to be 822 ± 3 G [7].In this paper we report on a detailed study of Feshbach resonances in 6 Li with the goal of accurately characterizing the interaction potential of two 6 Li atoms. Three resonances in the |1 and |2 states which are p-wave resonances have been observed [11]. The positions of these Feshbach resonances together with the location of a narrow s-wave resonance in the |1 + |2 mixture near 543 G are used for a precise determination of the singlet swave scattering length. These results, however, do not constrain the position of the broad resonance, which also depends on the triplet scattering length. An improved measurement of its location is presented and the magnitude and the origin of possible systematic errors are discussed.The experimental setup has been described in Ref. [12].Up to 4 × 10 7 quantum degenerate 6 Li atoms in the |F,m F = |3/2, 3/2 state were obtained in a magnetic trap by sympathetic cooling with 23 Na. The 6 Li atoms were then transferred into an optical dipole trap (ODT) formed by a 1064 nm laser beam with a maximum power of 9 W. In the optical trap three different samples were prepared: A single radio-frequency sweep transferred the atoms to state |1 (|F,m F = |1/2, 1/2 at low field). Another Landau-Zener sweep at an externally applied magnetic field of 565 G could then be used to either prepare the entire sample in state |2 (|1/2, −1/2 at low field) or create an equal mixture of atoms in state |1 and |2 . Except for the measurement of the broad s-wave Feshbach resonance, all resonances were observed by monitoring magnetic field dependent atom losses. Atom numbers were obtained from absorption images taken at zero field. The externally applied field was calibrated by driving microwave transitions from state |2 to state |5 (|3/2, 1/2 at low field) and from state |1 to state |6 (|3/2, 3/2 at low field) for several magnetic fields close to the resonance positions. For spin polarized samples either in state |1 or |2 swave scattering is forb...

Thermodynamics of Ultracold Fermi Gases

“…In order to produce a reversed magnetic curvature with the same coils, we suddenly reverse the bias magnetic eld, and then slowly ramp the bias up to B 0 = 834 G, and the curvature elds up to ω z /2π = 40 Hz (see Fig.2.7). About 20% of the atoms are lost in the process, and no signi cant atom loss is observed when crossing the p-wave Feshbach resonance at B 0 = 159 G [102,103]. Finally, a |1 -|2 mixture is created using a non-adiabatic Landau Zener passage around the nuclear spin-ip transition |1 →|2 at 76,4 MHz.…”

Heteropairing and component-dependent pseudogap phenomena in an ultracold Fermi gas with different species with different masses

“…Although no one has succeeded in this attempt, various possibilities have been so far explored, such as a p-wave superfluid [5][6][7][8][9][10][11][12][13], the Berezinskii-Kosterlitz-Thouless state [14][15][16][17][18], a superfluid state with hetero-Cooper-pairs , the Sarma phase [39,40,43,44], a Fermi superfluid with a spin-orbit interaction [45][46][47][48], and a dipolar Fermi superfluid [49,50]. Once one of them is realized, one could clarify its superfluid properties, maximally using the high tunability of Fermi gases [51] and various experimental techniques [52][53][54][55][56][57][58].…”

Superfluidity ofp-wave ands-wave atomic Fermi gases in optical lattices

“…However, the properties of SHS ultracold fermions and their possible superfluid behaviour are beginning to be investigated 30,31,32,33,34 . These systems are probably the next frontier for experiments with ultracold atoms.…”