Three-body crossover from a Cooper triple to bound trimer state in three-component Fermi gases near a triatomic resonance

Abstract

We theoretically investigate ground-state properties of a three-component Fermi gas with pairwise contact interactions between different components near a triatomic resonance where bound trimers are about to appear. Using variational equations for in-medium two-and three-body cluster states in three dimensions, we elucidate the competition of pair and triple formations due to the Fermi surface effects. We present the ground-state phase diagram that exhibits transition from a Cooper pair to Cooper triple state and crossover from a Cooper triple to tightly bound trimer state at negative scattering lengths. This three-body crossover is analogous to the Bardeen-Cooper-Schrieffer to Bose-Einstein condensation crossover observed in a two-component Fermi gas. We predict that the threshold scattering length a − for three-body states can be shifted towards the weak-coupling side due to the emergence of Cooper triples.

Cooper quartet correlations in infinite symmetric nuclear matter

“…Moreover, the theoretical framework of quartet correlations in infinite matter can be applied to other systems such as biexciton condensation [34,35], SU(4) Fermi atomic gases [36][37][38], and charge 4e superconductors [39,40]. In the context of interdisciplinary studies of multicomponent fermions, more than two-body cluster states induced by the Cooper instability [41][42][43][44][45][46][47] and groundstate properties and N -particle off-diagonal long-range order of η pairing in the attractive SU(N ) Hubbard model [48,49] have been studied theoretically. Also, the recent experiment indicates the existence of quartet correlations with broken time-reversal symmetry above the superconducting critical temperature in a condensedmatter system [50].…”