Dynamical properties of ultracold bosons in an optical lattice

S. D. Huber, E. Altman, H. P. Büchler, and G. Blatter
Phys. Rev. B 75, 085106 – Published 9 February 2007

Abstract

We study the excitation spectrum of strongly correlated lattice bosons for the Mott-insulating phase and for the superfluid phase close to localization. Within a Schwinger-boson mean-field approach we find two gapped modes in the Mott insulator and the combination of a sound mode (Goldstone) and a gapped (Higgs) mode in the superfluid. To make our findings comparable with experimental results, we calculate the dynamic structure factor as well as the linear response to the optical lattice modulation introduced by Stöferle et al. [Phys. Rev. Lett. 92, 130403 (2004)]. We find that the puzzling finite frequency absorption observed in the superfluid phase could be explained via the excitation of the gapped (Higgs) mode. We check the consistency of our results with an adapted f-sum rule and propose an extension of the experimental technique by Stöferle et al. to further verify our findings.

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  • Received 27 October 2006

DOI:https://doi.org/10.1103/PhysRevB.75.085106

©2007 American Physical Society

Authors & Affiliations

S. D. Huber1, E. Altman2, H. P. Büchler3,4, and G. Blatter1

  • 1Theoretische Physik, ETH Zurich, CH-8093 Zurich, Switzerland
  • 2Department of Condensed Matter Physics, The Weizmann Institute of Science, Rehovot, 76100, Israel
  • 3Institute for Quantum Optics and Quantum Information of the Austrian Academy of Science, 6020 Innsbruck, Austria
  • 4Institut für Theoretische Physik, Universität Innsbruck, 6020 Innsbruck, Austria

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Issue

Vol. 75, Iss. 8 — 15 February 2007

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