47 research outputs found
Momentum-resolved Raman spectroscopy of non-interacting ultracold Fermi gas
We report the experiment on probing the one-body spectral function in a
trapped non-interacting K Fermi gas by means of the momentum-resolved
Raman spectroscopy The experimental result is in good agreement with the
expected quadratic dispersion in the non-interacting regime. Through the
comparison with the radio-frequency spectrum, we found that the Raman spectrum
shows some new characteristics.Comment: 4 pages, 2 figures, appear in Phys. Rev.
Radio-frequency spectroscopy of a strongly interacting spin-orbit coupled Fermi gas
We investigate experimentally and theoretically radio-frequency spectroscopy
and pairing of a spin-orbit-coupled Fermi gas of K atoms near a Feshbach
resonance at G. Experimentally, the integrated spectroscopy is
measured, showing characteristic blue and red shifts in the atomic and
molecular responses, respectively, with increasing spin-orbit coupling.
Theoretically, a smooth transition from atomic to molecular responses in the
momentum-resolved spectroscopy is predicted, with a clear signature of
anisotropic pairing at and below resonance. Our many-body prediction agrees
qualitatively well with the observed spectroscopy near the Feshbach resonance.Comment: 7 pages, 4 figures. Supercedes 1302.055
Observation of collective atomic recoil motion in a momentum-squeezed, ultra-cold, degenerate fermion gas
We demonstrate clear collective atomic recoil motion in a dilute,
momentum-squeezed, ultra-cold degenerate fermion gas by circumventing the
effects of Pauli blocking. Although gain from bosonic stimulation is
necessarily absent because the quantum gas obeys Fermi-Dirac statistics,
collective atomic recoil motion from the underlying wave-mixing process is
clearly visible. With a single pump pulse of the proper polarization, we
observe two mutually-perpendicular wave-mixing processes occurring
simultaneously. Our experiments also indicate that the red-blue pump detuning
asymmetry observed with Bose-Einstein condensates does not occur with fermions
Word Familiarity Modulates the Interference Effects of Mind Wandering on Semantic and Reafferent Information Processing
It has been found that mind wandering interferes with the sensory and cognitive processing of widespread stimuli. However, it remains unclear what factors can modulate the magnitude of the interference effects of mind wandering. Here, we investigate whether and how word familiarity modulates the interference effects of mind wandering on semantic and reafferent information processing. High- and low-frequency words were used as stimuli to induce high- and low-familiarity contexts in a sustained attention to response task, in which participants were required to respond to Chinese nonanimal words (nontarget) and withhold responses to Chinese animal words (target) as well as to intermittently report whether their state was "on task" or "off task." Behavioral results revealed lower reaction stability for both high- and low-frequency nontarget words preceding "off-task" reports than those preceding "on-task" reports. However, ERP results revealed that low-frequency rather than high-frequency words elicited more negative N400, attenuated late positive complex, and attenuated reafferent potential for "off-task" reports than for "on-task" reports. The results suggest that mind wandering makes semantic extraction and integration more difficult for unfamiliar but not familiar two-character Chinese words and attenuates the reafferent feedback of the motor response. These findings are consistent with the decoupling hypothesis of mind wandering and provide the first neural evidence for how familiarity with external stimuli modulates the interference effects of mind wandering