Fermion Pairing Across a Dipolar Interaction Induced Resonance

Abstract

It is known from the solution of the two-body problem that an anisotropic dipolar interaction can give rise to s-wave scattering resonances, which are named dipolar interaction induced resonances (DIIR). In this Letter, we study the zero-temperature many-body physics of a two-component Fermi gas across a DIIR. In the low-density regime, it is very striking that the resulting pairing order parameter is a nearly isotropic singlet pairing and the physics can be well described by an s-wave resonant interaction potential with finite range conditions, despite the anisotropic nature of the dipolar interaction. The pairing energy is as strong as a unitary Fermi gas near a magnetic Feshbach resonance. In the high-density regime, the anisotropic effect plays an important role. We find phase transitions from singlet pairing to a state with mixed singlet and triplet pairing and then from mixed pairing to pure triplet pairing. The state with mixed pairing spontaneously breaks the time-reversal symmetry.

Bound states and expansion dynamics of interacting bosons on a one-dimensional lattice

“…In recent times, the possibility of observing bound states in a cold-atoms setup by means of dynamical probes has drawn a lot of attention, both theoretically [23] and experimentally [24]. The existence of a stable bound state is also the key ingredient for the phenomenon of induced resonances which are at the origin of the BEC-BCS crossover effect in atomic systems [25], in Fermi gases [26] as well for polar molecules [27]. Very recently, bound states have also entered the debate about equilibration and thermalization [28].…”

Weyl Superfluidity in a Three-Dimensional Dipolar Fermi Gas

“…(3)) has ultraviolet divergence [26]. The origin of the divergence can be attributed to the singularity of the dipolar interaction potential for large momentum, or equivalently for short distance.…”

“…The effects of the anisotropic dipolar interaction on the fermion many-body physics have been extensively investigated [23]. In particular, this provides the possibility of superfluid pairing between dipolar Fermi atoms in spinless or multicomponent systems [24][25][26][27] at low temperatures. For dipoles aligned parallel to the z direction, a p-wave superfluid state with the dominant p z symmetry was studied in a three-dimensional dipolar Fermi gas [28] and the competition between this superfluidity and nematic charge-density-wave (CDW) was also discussed [29].…”

Fermion superfluid with hybridized s- and p-wave pairings

“…For example, the coexistence of s-and p-wave pairings has been investigated in a fermion superfluid with long-range dipole-dipole interactions, which naturally contain all partial-wave components [23], or in a spin-imbalanced Fermi gas with swave interactions [24]. In these cases, the p-wave pairing is either spin independent [23], or driven by spin/density fluctuations and thus quite small in strength [24]. In our system, the induced p-wave pairing is due to the interplay of the s-and p-wave interactions, which gives rise to an appreciable pairing strength (see Fig.…”