Stable Higgs Modes in Fulde-Ferrell-Larkin-Ovchinnikov States

Andrzej Ptok

Matthias Eschrig

Alexandra Behrle, Timothy Harrison, Johannes Kombe +5 more

Shovan Dutta, Erich J. Mueller

We characterize the collective modes of a soliton train in a quasi-one-dimensional Fermi superfluid, using a mean-field formalism. In addition to the expected Goldstone and Higgs modes, we find novel long-lived gapped modes associated with oscillations of the soliton cores. The soliton train has an instability that depends strongly on the interaction strength and the spacing of solitons. It can be stabilized by filling each soliton with an unpaired fermion, thus forming a commensurate Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phase. We find that such a state is always dynamically stable, which paves the way for realizing long-lived FFLO states in experiments via phase imprinting.

Lei Zhang, Yinglong Ge, Xinle Shang +1 more

The Fulde–Ferrell–Larkin–Ovchinnikov (FFLO) state in asymmetric D-wave fermion superfluids is investigated generally. The angle dependence of the pairing gap (angle-dependent gap) for D-wave is also considered. Except the two special orientations of the Cooper pair momentum which are parallel/orthogonal to the symmetry-axis of ADG (called as FFLO-ADG-O and FFLO-ADG-P states), new orientations of the Cooper pair momentum between the two special ones are also found. These new orientations of the Cooper pair momentum correspond to new possible locally stable state (defined as FFLO-ADG-B state). Furthermore, the FFLO-ADG-O state is favored for small asymmetry and the FFLO-ADG-P state is located at large asymmetry, whereas the FFLO-ADG-B state is stable for moderate asymmetry. Moreover, the range of the asymmetry where the superfluids exists is enhanced strongly by taking the ADG to the FFLO state.

K. Gao, Alexandra Behrle, Timothy Harrison +5 more