Efimov physics in the presence of a Fermi sea

Abstract

Motivated by recent experiments on 6 Li-133 Cs atomic mixtures with high mass imbalance, we study the Efimov correlation in atomic system of two heavy bosons ( 133 Cs) immersed in a bath of light fermions ( 6 Li). Using the Born-Oppenheimer approximation, we identify two different regimes, depending on the Fermi momentum of light fermions (kF ) and the boson-fermion scattering length as(< 0), where the presence of underlying Fermi sea plays distinct roles in the Efimov-type binding of bosons. Namely, in the regime kF |as| 1 (kF |as| 1), the Fermi sea induces an attractive (repulsive) effective interaction between bosons and thus favors (disfavors) the formation of bound state, which can be seen as the Efimov trimer dressed by the fermion cloud. Interestingly, this implies a non-monotonic behavior of these bound states as increasing the fermion density (or kF ). Moreover, we establish a generalized universal scaling law for the emergence/variation of such dressed Efimov bound states when incorporating a new scale (kF ) brought by the Fermi sea. These results can be directly tested in Li-Cs cold atoms experiment by measuring the modified bound state spectrum and the shifted Efimov resonance, which manifest an emergent non-trivial Efimov correlation in a fermionic many-body environment.A main task of physics research is uncovering novel few-body correlations in interacting many-body systems. In 1970, Vitaly Efimov discovers an intriguing three-body effect, in which three identical bosons can form a sequence of bound states in the vicinity of two-body resonance and they satisfy a universal scaling law [1]. In recent years, the Efimov effect has been generalized to a variety of three-body systems with different statistics and mass ratios, and has also been verified in the ultracold gases of various atomic mixtures . Given these developments, it is time to move on to address the interplay of such novel three-body effect and a many-body environment. For instance, how to visualize the Efimov effect/correlation in a many-body system? and in turn, how would a many-body background change the Efimov physics? These are all very charming while highly challenging problems, because they are associated with nontrivial few-body correlations in the strongly interacting many-body systems.The polaron system, which consists of a few impurities immersed in a majority of other particles, can serve as the simplest platform for investigating the interplay problem between few and many. Depending on the statistics of majority particles, the system can be classified into Bose polarons and Fermi polarons, both having been realized in cold atoms experiments [23][24][25][26][27][28][29][30][31]. Theoretically, there have been a number of studies revealing the universal three-body correlations in Bose polaron and Fermi polaron systems [32][33][34][35][36][37][38][39][40][41][42][43][44][45][46]. Nevertheless, the experimental detection of three-body correlation in polaron systems still remains at its infancy [47].In this work, we reveal the Efim...

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

“…In this sense, the amplification of the three-body loss in the presence of the Fermi surface compared to the in-vacuum case could be a signature of the Cooper triple formation. Although such a shift originating from the Fermi sea has already been predicted in a different situation where two of three hyperfine states have Fermi seas [46,49,53], our result gives a physical interpretation based on the Cooper triple state. We note that the calculation of Γ is stopped at a = a m− (a = a − for the in-vacuum case) where the in-medium three-body bound state disappears.…”

“…While the Fermi degeneracy can be achieved experimentally [44], the superfluid state has not yet been realized due to the strong three-body loss near the Feshbach resonance. In this regard, numerous attention is paid to understand how the Efimov trimer behaves in the presence of Fermi seas [45][46][47][48][49][50][51][52][53]. Moreover, a unique crossover phenomenon involving superfluidity and trimer gases has been investigated [54][55][56][57][58].…”

Fermions Meet Two Bosons—the Heteronuclear Efimov Effect Revisited

“…1. Indeed, in the presence of the Fermi Sea, the two heavy bosons follow a new discrete scaling law including the additional length scale k F [12,14]: (n) − (λk F ), E n+1 (k F , a) = λ −2 E n (λk F , λ −1 a) (11) In the case of finite intraspecies interactions we find that this scaling is fulfilled for high-lying bound states n > 1 (inset of Fig. 5).…”

“…Similarly, one can consider the Efimov effect from a few-body perspective and study the influence of a surrounding many-body background to the trimer. The latter has been studied in different scenarios with either a Fermi Sea [12][13][14][15] or a BEC [16,17] serving as a background. The former has been studied in [18][19][20], following recent experimental advances in creating Bose [21][22][23][24][25] and Fermi polarons [26][27][28][29][30][31][32].…”

Condensation of Cooper Triples

“…In a three-component fermionic system, the formation of Cooper triples, which correspond to a three-body version of Cooper pairs, has been studied in the presence of two-body and three-body interactions [7,8]. It is also under investigation how medium corrections affect properties of Efimov trimers [9][10][11][12][13][14][15][16]. In addition, an inmedium cluster state consisting of more than three particles such as a Cooper quartet has also been pointed out [17,18].…”