Kavli Affiliate: Feng Yuan
| First 5 Authors: Peng Zou, Huaisong Zhao, Feng Yuan, Shi-Guo Peng,
| Summary:
We theoretically investigate a one-dimensional Fulde-Ferrell Fermi superfluid
at a finite effective Zeeman field $h$, and study entire dynamical excitations
related to density perturbation. By calculating the density dynamic structure
factor, we find anisotropic dynamical excitations in both collective modes and
single-particle excitations. Along the direction of centre-of-mass momentum
$p$, there are two obvious gapless collective modes with different speed. The
lower collective modes is from the usual gauge symmetry breaking and has a
larger speed than the one in the negative direction of $p$. The higher one is
due to the direction spontaneous symmetry breaking of centre-of-mass momentum
$p$, and separates two kinds of single-particle excitations in the positive $p$
direction. However, this higher mode disappears in the opposite direction of
$p$, where two single-particle excitations overlap with each other. These
signals of dynamical excitations can do help to distinguish Fulde-Ferrell
superfluid from the conventional Bardeen-Cooper-Schrieffer superfluid in the
future experiment.
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