Regensburg 2022 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 9: Cold Atomic Gases and Superfluids

TT 9.5: Talk

Monday, September 5, 2022, 19:00–19:15, H23

Out-of-equilibrium dynamics of bosons on a 2D Hubbard lattice — •Ulli Pohl, Sayak Ray, and Johann Kroha — Physikalisches Institut, Rheinische Friedrich-Wilhelms-Universität Bonn, Nußallee 12, 53115 Bonn, Germany

We study the collective excitations of bosons in two-dimensional optical Hubbard lattices, described by the Bose-Hubbard model, using the cluster mean field theory at zero temperature. The method has been shown to be very powerful to determine the phase boundaries both at zero and finite temperatures [1]. From the low-lying excitations, we identify the presence of the Higgs and the Goldstone modes of the superfluid, as well as the particle- and hole-like excitations in the Mott insulator phase and calculate their dispersion relations. The effective mass of the quasiparticles and -holes vanish at the tip of the Mott lobe where the Higgs energy gap also vanishes. Finally, we present the real time dynamics of the collective excitations, particularly, the Higgs mode. Our findings, particularly the dynamics of excitations support the previous mean-field-like calculations and can be relevant for cold-atom experiments.
[1] U. Pohl, S. Ray, J. Kroha arXiv:2106.14860