Hannover 2013 – wissenschaftliches Programm
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Q: Fachverband Quantenoptik und Photonik
Q 56: Poster III
Q 56.33: Poster
Donnerstag, 21. März 2013, 16:00–18:30, Empore Lichthof
Intrinsic Photoconductivity of Ultracold Fermions in Optical Lattices — •Jannes Heinze1, Jasper Simon Krauser1, Nick Fläschner1, Bastian Hundt1, Sören Götze1, Alexander Itin1,2,3, Ludwig Mathey1,2, Klaus Sengstock1,2, and Christoph Becker1,2 — 1Institut für Laser-Physik, Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany — 2Zentrum für Optische Quantentechnologien, Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany — 3Space Research Institute, Russian Academy of Sciences, Moscow, Russia
Photoconductivity describes the change of a material’s conductivity following an excitation with photons. If the photon energy is resonant with a band transition, electrons are excited from the valence band to the conduction band and an initial insulator becomes conducting. We present measurements of an analog to a persistent alternating photocurrent in an ultracold gas of fermionic atoms in an optical lattice (arXiv:1208.4020). A small fraction of the atoms is excited to the second excited band using lattice amplitude modulation, leaving holes in the lowest band. Both hole and particle excitations have a defined quasimomentum. The subsequent dynamics is induced and sustained by an external harmonic confinement. While atoms in the excited band exhibit long-lived oscillations with a momentum dependent frequency a strikingly different behavior is observed for holes in the lowest band. An initial fast collapse is followed by subsequent periodic revivals. Both observations are fully explained by mapping the system onto a nonlinear pendulum. This work is supported by DFG within FOR801.