Symmetry-broken momentum distributions induced by matter-wave diffraction during time-of-flight expansion of ultracold atoms

摘要

We study several effects which lead to symmetry-broken momentum distributionsof quantum gases released from optical lattices. In particular, we demonstratethat interaction within the first milliseconds of the time-of-flight expansioncan strongly alter the measurement of the initial atomic momentum distribution.For bosonic mixtures in state-dependent lattices, inter-species scatteringprocesses lead to a symmetry breaking in momentum space. The underlyingmechanism is identified to be diffraction of the matter wave from the totaldensity lattice, which gives rise to a time-dependent interaction potential.Our findings are of fundamental relevance for the interpretation oftime-of-flight measurements and for the study of exotic quantum phases such asthe twisted superfluid. Beyond that, the observed matter-wave diffraction canalso be used as an interferometric probe. In addition, we report on diffractionfrom the state-dependent standing light field, which leads to the samesymmetry-broken momentum distributions, even for single component condensates.