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TT: Fachverband Tiefe Temperaturen
TT 37: MLT: Quantum Liquids, Bose-Einstein Condensates, Ultra-cold Atoms, ...
TT 37.7: Talk
Wednesday, March 16, 2011, 15:45–16:00, HSZ 105
Detecting the Amplitude Mode of Strongly Interacting Lattice Bosons by Bragg Scattering — •Ulf Bissbort1, Yongqiang Li1, Sören Götze2, Jannes Heinze2, Jasper S. Krauser2, Malte Weinberg2, Christoph Becker2, Klaus Sengstock2, and Walter Hofstetter1 — 1Institut für Theoretische Physik, Johann Wolfgang Goethe Universität, 60438 Frankfurt/Main — 2Institut für Laser-Physik, Universität Hamburg, 22761 Hamburg
We report the first detection of the Higgs-type amplitude mode using Bragg spectroscopy in a strongly interacting condensate of ultracold atoms in an optical lattice. By the comparison of our experimental data with a spatially resolved, time-dependent dynamic Gutzwiller calculation, we obtain good quantitative agreement. This allows for a clear identification of the amplitude mode, showing that it can be detected with full momentum resolution by going beyond the linear response regime. A systematic shift of the sound and amplitude modes' resonance frequencies due to the finite Bragg beam intensity is observed. Within an extended Bogoliubov-de Gennes approach, an extensive quasi-particle analysis of the dynamical processes during the spectroscopic measurement is presented.