Speaker
Walter Hofstetter (Goethe-Universität Frankfurt)
Description
Cold atoms in optical lattices offer a new laboratory for
the study of
strong correlation phenomena.I will focus on two recent
developments:
i) We report the first detection of the Higgs-type amplitude
mode using Bragg spectroscopy
in a strongly interacting Bose condensate in an optical
lattice. By the comparison of our experimental data
with a spatially resolved, dynamical 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.
ii) We investigate antiferromagnetic ordering of trapped
spin-1/2 fermions
using large-scale dynamical mean-field theory simulations.
We find a clear experimental signature - enhanced double
occupancy -
for the onset of magnetic order at low temperatures in
current experiments.
We also discuss the effect of spin imbalance leading to
canted antiferromagnetism.
