Excitons and polaritons for optical lattice ultracold atoms |
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| Hashem Zoubi | |
| Innsbruck University | |
| We introduce excitons and cavity polaritons into a system of optical lattice ultracold atoms [1]. Ultracold ground state atoms in optical lattices realize the quantum phase transition from the superfluid to the Mott insulator phase, which is predicted by the Bose-Hubbard model. We extend the model to include electronically excited atoms and their resonant coupling to cavity photons. In applying mean field theory we calculate the new phase diagram, where the Mott insulator phase reappears for deeper optical lattices [2]. In the Mott insulator phase with a fixed number of atoms per site we consider the system as an artificial crystal, similar to molecular crystals with advantages due to the wide controllability of the system parameters. In such a system electronic excitations are delocalized due to resonance dipole-dipole interactions and in exploiting the lattice symmetry they form collective electronic excitations (excitons), where excitons are safe for the Mott insulator phase with suppressed recoil effect. Excitons in low dimensional systems include dark and bright modes, and in free space they can be metastable or superradiant, which strongly deviates from the case of a single excited atom. We suggest optical lattice ultracold atoms as new a frontier of matter for cavity QED. In the strong coupling regime excitons and cavity photons are coherently mixed to form polaritons [3]. We present different set-ups that have the potential to realize optical lattice ultracold atoms within a cavity. We emphasize the recent experiment in using tapered nanofibers, which are simultaneously used to trap and optically interface cold atoms through evanescent fields [4]. [1] H Zoubi, H Ritsch, PRA 76, 013817 (2007). [2] H Zoubi, H Ritsch, PRA 80, 053608 (2009). [3] H Zoubi, H Ritsch, EPL 87, 23001 (2009). [4] H Zoubi, H Ritsch, NJP 12, 103014 (2010). |