Dresden 2011 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 37: MLT: Quantum Liquids, Bose-Einstein Condensates, Ultra-cold Atoms, ...

TT 37.9: Vortrag

Mittwoch, 16. März 2011, 16:15–16:30, HSZ 105

Correlated Bosons beyond Pairwise Interactions - Dimersuperfluid in Two Dimensions — •Lars Bonnes and Stefan Wessel — Institut für Theoretische Physik III, Pfaffenwaldring 57, 70550 Stuttgart, Germany

We consider ultra-cold atoms loaded into a two-dimensional optical lattice with strong three-body losses, i.e. three bosons sharing one lattice site scatter inelastically and dissipate from the system. This process dynamically stabilizes a three-body on-site repulsion in analogy to the quantum Zeno effect. The system studied here is described by a Bose-Hubbard model on a square lattice with on-site attraction. The maximal number of particles per lattice site is restricted to two in order to take the three-body repulsion into account. Field theoretical considerations and numerical simulations using Matrix Product States in one dimension suggest the existence of a dimer superfluid phase for small tunneling rates that is effectively described by the condensation of pairs bosons and the absence of an atomic condensate. In this work we explore the ground state and finite-temperature phase diagram for our model using large-scale quantum Monte-Carlo simulations. Our main emphasis is the detection of the dimer superfluid phase and we address the issue of extrapolating our finite-temperature data to the thermodyanmic limit at T=0. We address the numerical issues i.e., fat-tailed distributions in the condensate density and demonstrate how we are able to overcome this issue by adding a term that couples lineary to the order parameter leading to a system with arbitrary long-range pair-hopping processes.