"A Free Space Self-Ordered Atom-Photon Crystal" Event as iCalendar

13 February 2017

2 - 3pm

Venue: 303-610

Speaker: H. Ritsch, Institut für Theoretische Physik, Universität Innsbruck, Austria

Title: "A Free Space Self-Ordered Atom-Photon Crystal"

Abstract: The dispersive interaction of a cold gaseous medium with electromagnetic waves involves an exchange of energy and momentum leads to a wealth of intriguing nonlinear dynamical phenomena. A prominent example is self-ordering, whereby the particles spontaneously form stationary periodic structures, simultaneously maximising Bragg scattering and minimizing their potential energy. This has been experimentally observed with thermal gases and more recently also with Bose-Einstein condensates (BECs) inside optical resonators. The latter selects a discrete set of electromagnetic modes so that self-ordering leads to discrete symmetry breaking.

As a new regime we study steady-state self-ordering with a driven BEC in a free-space configuration, where no pre-selected wave vectors are imposed by the mirror boundary conditions. Hence self-ordering amounts to a crystallization breaking a continuous symmetry and showing an intrinsic length scale. In the self-ordered phase both matter and light crystallize: the BEC into a supersolid and the light field into an optical standing wave pattern. As a decisive signature of crystallization the close to infinite range atomic interactions generate a gapped acoustic phonon branch.