Thursday, March 8, 2012

1203.1322 (R. Mottl et al.)

Observation of roton-type mode softening in a quantum gas with
cavity-mediated long-range interactions
   [PDF]

R. Mottl, F. Brennecke, K. Baumann, R. Landig, T. Donner, T. Esslinger
Long-range interactions in quantum gases are predicted to give rise to a roton spectrum, as known from superfluid helium. We investigate the excitation spectrum of a Bose-Einstein condensate with cavity-mediated long-range interactions, which couple all particles to each other. Increasing the strength of the interaction leads to a softening of an excitation mode at a finite momentum, preceding a superfluid to supersolid phase transition. The mode softening is spectroscopically studied across the phase transition using a variant of Bragg spectroscopy. At the phase transition, a diverging susceptibility is observed. Very good agreement with ab initio calculations is found. The work paves the way towards quantum simulation of long-range interacting many-body systems.
View original: http://arxiv.org/abs/1203.1322

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