75,668 research outputs found
Momentum-resolved radio-frequency spectroscopy of ultracold atomic Fermi gases in a spin-orbit coupled lattice
We investigate theoretically momentum-resolved radio-frequency (rf)
spectroscopy of a noninteracting atomic Fermi gas in a spin-orbit coupled
lattice. This lattice configuration has been recently created at MIT [Cheuk et
al., arXiv:1205.3483] for 6Li atoms, by coupling the two hyperfine spin-states
with a pair of Raman laser beams and additional rf coupling. Here, we show that
momentum-resolved rf spectroscopy can measure single-particle energies and
eigenstates and therefore resolve the band structure of the spin-orbit coupled
lattice. In our calculations, we take into account the effects of temperatures
and harmonic traps. Our predictions are to be confronted with future
experiments on spin-orbit coupled Fermi gases of 40K atoms in a lattice
potential.Comment: 9 pages, 8 figure
Impurity probe of topological superfluid in one-dimensional spin-orbit coupled atomic Fermi gases
We investigate theoretically non-magnetic impurity scattering in a
one-dimensional atomic topological superfluid in harmonic traps, by solving
self-consistently the microscopic Bogoliubov-de Gennes equation. In sharp
contrast to topologically trivial Bardeen-Cooper-Schrieffer \textit{s}-wave
superfluid, topological superfluid can host a mid-gap state that is bound to
localized non-magnetic impurity. For strong impurity scattering, the bound
state becomes universal, with nearly zero energy and a wave-function that
closely follows the symmetry of that of Majorana fermions. We propose that the
observation of such a universal bound state could be a useful evidence for
characterizing the topolgoical nature of topological superfluids. Our
prediction is applicable to an ultracold resonantly-interacting Fermi gas of
K atoms with spin-orbit coupling confined in a two-dimensional optical
lattice.Comment: 9 pages, 8 figure
Fulde-Ferrell pairing instability of a Rashba spin-orbit coupled Fermi gas
We theoretically analyze the pairing instability of a three-dimensional
ultracold atomic Fermi gas towards a Fulde-Ferrell superfluid, in the presence
of Rashba spin-orbit coupling and in-plane Zeeman field. We use the standard
Thouless criterion for the onset of superfluidity, with which the effect of
pair fluctuations is partially taken into account by approximately using a
mean-field chemical potential at zero temperature. This gives rise to an
improved prediction of the superfluid transition temperature beyond mean-field,
particularly in the strong-coupling unitary limit. We also investigate the
pairing instability with increasing Rashba spin-orbit coupling, along the
crossover from a Bardeen-Cooper-Schrieffer superfluid to a Bose-Einstein
condensate of Rashbons (i.e., the tightly bound state of two fermions formed by
strong Rashba spin-orbit couplingComment: 8 pages, 9 figure
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