Frustrated orbital Feshbach resonances in a Fermi gas

Abstract

The orbital Feshbach resonance (OFR) is a novel scheme for magnetically tuning the interactions in closed-shell fermionic atoms. Remarkably, unlike the Feshbach resonances in alkali atoms, the open and closed channels of the OFR are only very weakly detuned in energy. This leads to a unique effect whereby a medium in the closed channel can Pauli block -or frustrate -the twobody scattering processes. Here, we theoretically investigate the impact of frustration in the fewand many-body limits of the experimentally accessible three-dimensional 173 Yb system. We find that by adding a closed-channel atom to the two-body problem, the binding energy of the ground state is significantly suppressed, and by introducing a closed-channel Fermi sea to the many-body problem, we can drive the system towards weaker fermion pairing. These results are potentially relevant to superconductivity in solid-state multiband materials, as well as to the current and continuing exploration of unconventional Fermi-gas superfluids near the OFR. arXiv:1908.04495v1 [cond-mat.quant-gas]

Clock-line photoassociation of strongly bound dimers in a magic-wavelength lattice

“…In the case of an interorbital interaction potential, this leads to orbital Feshbach resonances (OFR) [18], until now only observed in 173 Yb [19,20]. This novel type of Feshbach resonance allows to tune contact interactions between |g and |e atoms, and has enabled the realization of multiorbital Fermi polarons [13], coherent preparation of weakly bound dimers on the clock transition [21], and has inspired multiple proposals for the realization of exotic superfluidity [22][23][24].…”

Controlling the interaction of ultracold alkaline-earth atoms

“…This forces us to take into account the scattering state in the closed channel, that is to say, the so-called closed channel is not really "closed". The multi-orbital nature brings the physics into a new parameter regime that has not been explored before [39,[58][59][60][61][62][63][64][65][66][67][68][69][70][71][72][73]. Here we simply give couple examples.…”

“…First of all, the strong influence of the closed channel leads to a strong momentum dependence of the scattering amplitude, which can lead to an even higher transition temperature for forming Fermi superfluid, comparing to the single-channel wide resonance in alkaline-metal atom [58]. In the superfluid phase, since both two channels are occupied by the scattering states, it requires two order pairing order parameters to describes such a Fermi superfluid, which adds a new twist to the BEC-BCS crossover physics [39,[58][59][60][61][62][63][64][65]. This is reminiscent of multi-band superconductor in solid-state materials.…”

Superfluid properties of an ultracold Fermi gas with an orbital Feshbach resonance in the BCS-BEC crossover region

“…Since the proposal of a Feshbach resonance using the orbital degrees of freedom in 2015 [1], this so-called orbital Feshbach resonance (OFR) has attracted much attention as a candidate for the pairing mechanism of a 173 Yb Fermi gas [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. Although the superfluid phase transition of this alkaline-earth-like Fermi gas has not been realized yet, experimental groups have succeeded in tuning the strength of a pairing interaction between 173 Yb atoms, by adjusting the threshold energy of OFR [17,18].…”