# Dynamical Quasicondensation of Hard-Core Bosons at Finite Momenta

Presented by:
Ulrich Schneider University of Cambridge, Ludwig-Maximilians-Universität München, Max-Planck-Institut für Quantenoptik
Date:
Tuesday 12th January 2016 - 10:00 to 11:00
Venue:
INI Seminar Room 1
Abstract:
We experimentally study the expansion of initially localized ultracold bosons in homogeneous optical lattices in real and momentum space and find that both dimensionality and interaction strength crucially influence these out-of-equilibrium dynamics. While the atoms expand ballistically in all integrable limits, deviations from these limits dramatically suppress the expansion and lead to the appearance of almost bimodal real-space density distributions. For strongly interacting bosons, we observe a dimensional crossover of the dynamics from ballistic in the one-dimensional hard-core case to diffusive in two dimensions, as well as a similar crossover when higher occupancies are introduced into the system. Studying the same expansion in momentum space, we observe the onset of quasicondensation of expanding hard-core bosons at finite momenta in a high energy far-from-equilibrium situation, even though long-range order is usually associated with low-temperature equilibrium situations. In particular, we observe the emergence of peaks at finite momenta that corresponds to the spontaneous formation of coherence with a phase order that differs from the ground-state order.