4,938 research outputs found
Band Gap Closing in a Synthetic Hall Tube of Neutral Fermions
We report the experimental realization of a synthetic three-leg Hall tube
with ultracold fermionic atoms in a one-dimensional optical lattice. The legs
of the synthetic tube are composed of three hyperfine spin states of the atoms,
and the cyclic inter-leg links are generated by two-photon Raman transitions
between the spin states, resulting in a uniform gauge flux penetrating
each side plaquette of the tube. Using quench dynamics, we investigate the band
structure of the Hall tube system for a commensurate flux .
Momentum-resolved analysis of the quench dynamics reveals that a critical point
of band gap closing as one of the inter-leg coupling strengths is varied, which
is consistent with a topological phase transition predicted for the Hall tube
system.Comment: 8 pages, 8 figure
Double resonance of Raman transitions in a degenerate Fermi gas
We measure momentum-resolved Raman spectra of a spin-polarized degenerate
Fermi gas of Yb atoms for a wide range of magnetic fields, where the
atoms are irradiated by a pair of counterpropagating Raman laser beams as in
the conventional spin-orbit coupling scheme. Double resonance of first- and
second-order Raman transitions occurs at a certain magnetic field and the
spectrum exhibits a doublet splitting for high laser intensities. The measured
spectral splitting is quantitatively accounted for by the Autler-Townes effect.
We show that our measurement results are consistent with the spinful band
structure of a Fermi gas in the spatially oscillating effective magnetic field
generated by the Raman laser fields.Comment: 7 pages, 6 figure
Observation of a Geometric Hall Effect in a Spinor Bose-Einstein Condensate with a Skyrmion Spin Texture
For a spin-carrying particle moving in a spatially varying magnetic field,
effective electromagnetic forces can arise due to the geometric phase
associated with adiabatic spin rotation of the particle. We report the
observation of a geometric Hall effect in a spinor Bose-Einstein condensate
with a skyrmion spin texture. Under translational oscillations of the spin
texture, the condensate resonantly develops a circular motion in a harmonic
trap, demonstrating the existence of an effective Lorentz force. When the
condensate circulates, quantized vortices are nucleated in the boundary region
of the condensate and the vortex number increases over 100 without significant
heating. We attribute the vortex nucleation to the shearing effect of the
effective Lorentz force from the inhomogeneous effective magnetic field.Comment: 9 pages, 11 figure
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