Fermion superfluid with hybridized s- and p-wave pairings

Abstract

Ever since the pioneering work of Bardeen, Cooper and Schrieffer in the 1950s, exploring novel pairing mechanisms for fermion superfluids has become one of the central tasks in modern physics. Here, we investigate a new type of fermion superfluid with hybridized s-and p-wave pairings in an ultracold spin-1/2 Fermi gas. Its occurrence is facilitated by the co-existence of comparable s-and p-wave interactions, which is realizable in a two-component 40 K Fermi gas with close-by s-and p-wave Feshbach resonances. The hybridized superfluid state is stable over a considerable parameter region on the phase diagram, and can lead to intriguing patterns of spin densities and pairing fields in momentum space. In particular, it can induce a phase-locked p-wave pairing in the fermion species that has no p-wave interactions. The hybridized nature of this novel superfluid can also be confirmed by measuring the s-wave and p-wave contacts, which can be extracted from the high-momentum tail of the momentum distribution of each spin component. These results enrich our knowledge of pairing superfluidity in Fermi systems, and open the avenue for achieving novel fermion superfluids with multiple partial-wave scatterings in cold atomic gases.

Universal relations for hybridized s - and p -wave interactions from spin-orbital coupling

“…We consider a fermion system with an s-wave interaction between atoms with spin ↑ and ↓, together with a p-wave interaction between two spin-↑ fermions. Without SOC, the interesting few-and many-body physics have been studied in [67][68][69][70][71]. After adding the SOC, the effective 1D Lagrangian is given by (h = 1 throughout the paper)…”

s -wave contacts of quantum gases in quasi-one-dimensional and quasi-two-dimensional traps

“…are always valid in a quasi-1D trap; (II) Equations ( 4) and ( 5) establish exact relations between {C 1D , C 1 1D } and {C 3D , C 1 3D }; (III) As mentioned earlier, {a 3D , r e 3D } and {a 1D , r e 1D } are related by Eqs. (19) and (20). Thus, by simply taking Eqs.…”

“…The study of contacts and universal relations has provided physicists with a powerful tool to explore connections between two-body physics and many-body correlations in quantum gases and related systems. Since the first discovery by Shina Tan in 2005 [1][2][3], the concept of contacts and universal relations has been generalized to quantum systems for arbitrary partial wave scatterings in three-dimensional (3D) systems in different ways [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22]. Meanwhile, the generalization to strictly one-dimensional (1D) [24][25][26][27][28] and two-dimensional (2D) [29][30][31][32][33][34][35] quantum systems has also been explored.…”

Anapole superconductivity from $\mathcal{PT}$-symmetric mixed-parity interband pairing

“…In particular, mixed-parity superconductivity with coexistent even-and odd-parity pairing channels has been widely discussed in noncentrosymmetric superconductors [6,7], ultracold fermion systems [8,9], and spin-orbit-coupled systems in the vicinity of the P-symmetry breaking [10][11][12][13][14]. The P-symmetry is broken in such superconductors, and spontaneous T -symmetry breaking realized by the ±𝜋/2 phase difference between even-and odd-parity pairing potentials is energetically favored [15,16] (Fig.…”