Manipulating Cooper pairs with a controllable momentum in periodically driven degenerate Fermi gases

Abstract

We here present an experimentally feasible proposal for manipulating Cooper pairs in degenerate Fermi gases trapped by an optical lattice. Upon introducing an in situ periodically driven field, the system may be described by an effective time-independent Hamiltonian, in which the Cooper pairs, generated by the bound molecule state in Feshbach resonance, host a nonzero center-ofmass momentum. The system thus processes a crossover from a Bardeen-Cooper-Schrieffer (BCS) superfluid phase to a Fulde-Ferrell (FF) one. Furthermore, the magnitude and direction of the Cooper pairs in the synthetic FF superfluids are both directly controllable via the periodically driven field. Our proposal offers a reliable and feasible scenario for manipulating the Cooper pairs in cold atoms, serving as a tunable as well as powerful platform for quantum-emulating and exploring the FF superfluid phase. * zhenzhen.dr@hku.hk † zwang@hku.hk

Feshbach resonances of nonzero partial waves at different collision energies

“…Magnetically tuned Feshbach resonances (MFRs) [1][2][3][4][5][6][7][8][9][10][11][12][13][14] provide a tool for modulating the interaction between ultracold atoms or molecules. The scattering length can be modulated by a magnetic field to vary from positive to negative infinities in the vicinity of s-wave Feshbach resonance, which facilitates the observation and evaluation of the Bose-Einstein-condensation-Bardeen-Cooper-Schrieffer (BEC-BCS) crossover [15][16][17][18], BEC [19][20][21][22] and superfluid [23][24][25][26][27]. The centrifugal potential barrier suppresses the scattering of nonzero partial waves [5], and nonzero partial-wave resonances are narrow.…”

Cavity-induced Fulde-Ferrell-Larkin-Ovchinnikov superfluids of ultracold Fermi gases

“…This is the essential distinction from the ordinary zero-momentum pairing. Though there is a lack of prominent evidences in condensed-matter physics, various schemes have been proposed to synthesize and demonstrate this unconventional state in ultracold Fermi gases by using artificial fields [15][16][17][18][19][20][21][22][23][24][25][26][27][28].…”

Effective Hamiltonian with tunable mixed pairing in driven optical lattices

“…In order to generate independently tunable mixed pairing, we propose a scheme based on Floquet engineering [30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48] in this paper. Floquet engineering has proven to be a versatile method for realizing a variety of unconventional effective Hamiltonians with tunable parameters, for instance, correlated tunneling [42,49], spin-exchange interaction [50,51], and artificial gauge fields [52,53].…”