July 20 2015

20.-22.07.2015: Visit of Nishant Dogra

Nishant Dogra (Quantum Optics Group, ETH Zurich) is visiting us and will give a talk in our Ctrl-q seminar on Wednesday 22.07.2015 at 9.00 o'clock in E.04 about "Bose-Hubbard model with cavity-mediated long-range interactions: theory and experiment".


The Bose-Hubbard model has been a paramount example of quantum simulation of many-body
systems. It is realized by loading a quantum gas in a 3D optical lattice. This system undergoes a
quantum phase transition from a superfluid to a Mott-insulator phase due to the competition
between the kinetic energy and the short-range interactions. We study the effect of long-range
interactions on this system generated by strongly coupling the quantum gas to a high finesse cavity
and pumping it with a transverse laser field. This system can be mapped to an extended BoseHubbard
model. In the limit where the static lattices are commensurate with the cavity generated
dynamical lattice, we calculate the phase diagram of this system using a mean-field method. We find
that the cavity-mediated long-range interactions give rise to additional phases: charge density wave
and supersolid phase. We also calculate the excitation spectrum of these phases using a slave-Boson
approach and relate it to the nature of the transition between them. We also show the recent
experimental progress in observing the charge density wave and mapping the phase diagram of such
a system as a function of short-range and cavity-mediated long-range interactions.

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