1211.5162 (Kuei Sun et al.)

Pair tunneling, phase separation and dimensional crossover in imbalanced
fermionic superfluids in a coupled array of tubes    [PDF]

Kuei Sun, C. J. Bolech

We study imbalanced fermionic superfluids in an array of one dimensional tubes at the incipient dimensional crossover regime, wherein particles can tunnel between neighboring tubes. In addition to single-particle tunneling (ST), we consider pair tunneling (PT) that incorporates the interaction effect during the tunneling process. We find that with an increase of PT strength, a system of low global polarization evolves from a structure with a central Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state to one with a central BCS-like fully-paired state. For the case of high global polarization, the center region exhibits pairing zeros embedded in a fully-paired order. In both cases, PT enhances the pairing gap, suppresses the FFLO order and leads to spatial separation of fully-paired and fully-polarized regions, same as in higher dimensions. Thus, we show that PT rather than ST is essential for the development of signatures characteristic of the incipience of the dimensional crossover.

View original: http://arxiv.org/abs/1211.5162