Hannover 2013 – wissenschaftliches Programm
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A: Fachverband Atomphysik
A 32: Ultra-cold atoms, ions and BEC VI (with Q)
A 32.6: Vortrag
Donnerstag, 21. März 2013, 12:15–12:30, B 305
Thermally induced coherent collapse of dipolar Bose-Einstein condensates — •Andrej Junginger1, Jörg Main1, Günter Wunner1, and Thomas Bartsch2 — 11. Institut für Theoretische Physik, Universität Stuttgart, Germany — 2Department of Mathematical Sciences, Loughborough University, UK
We investigate Bose-Einstein condensates (BECs) with additional anisotropic and long-range dipolar interaction at finite temperature. The ground state of such a system is metastable and one decay mechanism is the BEC’s coherent collapse due to collective thermal excitations. With focus on the latter and as an alternative to solving the Hartree-Fock-Bogoliubov equations, we make use of a variational approach to calculate the corresponding decay rates at temperatures small compared to the critical temperature. Within this variational approach, the collectively excited states of the condensates which form the “activated complex” are accessible. Using a normal form expansion of the equations of motion and the energy functional, the variational parameters can be mapped to classical phase space which allows for the application of transition-state theory. We show that the collapse dynamics of the dipolar BEC breaks the symmetry of the external trap if it is confined cylindrically symmetrical and present thermal decay rates for different temperatures of the quantum gas obtained from a variational ansatz using coupled Gaussian orbitals.