Hannover 2013 – wissenschaftliches Programm
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Q: Fachverband Quantenoptik und Photonik
Q 31: Quantum gases: Optical lattices I
Q 31.2: Vortrag
Dienstag, 19. März 2013, 14:30–14:45, E 001
Semiclassical Study of Intrinsic Photoconductivity of Ultracold Fermions in Optical Lattices — •Alexander Itin1,2,3, Jannes Heinze1, Jasper Simon Krauser1, Nick Fläschner1, Bastian Hundt1, Sören Götze1, Klaus Sengstock1,2, Christoph Becker1,2, and Ludwig Mathey1,2 — 1Institut für Laser-Physik, Universität Hamburg, Germany — 2Zentrum für Optische Quantentechnologien, Universität Hamburg, Germany — 3Space Research Institute, Moscow, Russia
We present theoretical analysis of recent experiments reported in [J. Heinze et al., arxiv::1208.4020v2]. Ultracold fermionic atoms in optical lattices were used to simulate the phenomenon of photoconductivity. Using amplitude modulations of the optical lattice, the analog of a persistent alternating photocurrent was induced in the atomic gas. A small fraction of the atoms was excited to the third band as a wavepacket with a well-defined quasimomentum, leaving a hole in the momentum distribution of atoms in the lowest band. The subsequent dynamics is due to an external harmonic trap. It was observed that the particle excitations in the third band exhibit long-lived oscillations with a frequency determined by the initial quasimomentum, while holes in the lowest band behave strikingly differently: an initial fast collapse was followed by periodic partial revivals. We explain both observations by a semiclassical approach to lattice dynamics. By using the Truncated Wigner Approximation and mapping the system onto a classical Hamiltonian resembling a nonlinear pendulum, both the long-lived particle oscillations and decaying hole revivals are understood quantitavely.