Physics at Virginia

"Photons as phonons: from cavity QED to quantum crystallization"

Sarang Gopalakrishnan , Urbana-Champaign
[Host: Austen Lamacraft]
Atoms in a transversely pumped optical cavity coherently scatter light between the pumping laser and the cavity mode(s) with a position-dependent intensity and phase; thus, the optical dipole potential created and experienced by an atom depends on its position in the cavity. For a single-mode cavity containing many atoms, the optical potential felt by each atom depends on the positions of all the other atoms; in this sense, the cavity mediates an infinite-range interatomic interaction with an oscillating sign. In cavities with many degenerate modes, one can realize more local interactions; these give rise to the crystallization of a Bose-Einstein condensate in a multimode cavity through a fluctuation-driven first-order quantum phase transition. This transition is described by a theory involving a nested surface of low-lying excitations, and is accompanied by a condensation of photons into one or more cavity modes. The resulting ordered state is a “supersolid,” i.e., a superfluid that spontaneously breaks a continuous translational symmetry. We discuss the nature of fluctuations near the transition and low-energy excitations in the ordered state, and prospects for their experimental detection.
Condensed Matter Seminar
Thursday, February 10, 2011
3:30 PM
Physics Building, Room 204
Note special room.

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