Hannover 2016 – wissenschaftliches Programm
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A: Fachverband Atomphysik
A 23: Ultra-cold atoms, ions and BEC I (with Q)
A 23.1: Vortrag
Mittwoch, 2. März 2016, 11:00–11:15, f107
Polaronic effects in one- and two-band quantum systems — •Tao Yin1, Daniel Cocks2, and Walter Hofstetter1 — 1Institut für Theoretische Physik, Johann Wolfgang Goethe-Universität, 60438 Frankfurt/Main, Germany — 2College of Science, Technology & Engineering, James Cook University, Townsville 4810, Australia
In this work we study the formation and dynamics of polarons in a system with a few impurities in a lattice immersed in a Bose-Einstein condensate (BEC). This system has been experimentally realized using ultracold atoms and optical lattices. Here we consider a two-band model for the impurity atoms, along with a Bogoliubov approximation for the BEC, with phonons coupled to impurities via both intra- and inter-band transitions. We decouple this Fröhlich-like term by an extended two-band Lang-Firsov polaron transformation using a variational method. The new effective Hamiltonian with two (polaron) bands differs from the original Hamiltonian by modified coherent transport, polaron energy shifts and induced long-range interaction. A Lindblad master equation approach is used to take into account residual incoherent coupling between polaron and bath. This polaronic treatment yields a renormalized inter-band relaxation rate compared to Fermi’s Golden Rule. For a strongly coupled two-band Fröhlich Hamiltonian, the polaron is tightly dressed in each band and can not tunnel between them, leading to an inter-band self-trapping effect.
[1] T. Yin, D. Cocks and W. Hofstetter, arXiv:1509.08283 (2015).