28. 11. 2012. Seminar: Dennis Hinrichs

Wednesday 28 November 2012 at 3PM
IPB Library

Dr. Dennis Hinrichs
University of Oldenburg, Germany

Abstract:

A few years after the first realization of a Bose-Einstein condensate many experiments focused on ultracold atoms in optical lattices. For bosons such a system is described by the Bose-Hubbard Hamiltonian which exhibits a quantum phase transition from a Mott insulator to a superfluid state. We study the critical properties of this quantum phase transition at zero temperature. By converting Kato's perturbation series into an efficient numerical algorithm and by applying the non-perturbative method of the effective potential, we gain access to the phase boundary as well as the superfluid and the condensate density. Based on this procedure we are also able to determine reliable values of their respective critical exponents via two different approaches. Whereas for the first approach we use variational perturbation theory in order to resum our raw data, the second approach allows the calculation of the critical exponents by using a numerical extrapolation scheme with no further resummation.