title: Amplitude mode in the quantum phase model.
abstract: We derive the collective low-energy excitations of the quantum phase model of interacting lattice bosons within the superfluid state using a dynamical variational approach. We recover the well-known sound (or Goldstone) mode and derive a gapped (Higgs-type) mode that was overlooked in previous studies of the quantum phase model. This mode is relevant to ultracold atoms in a strong optical lattice potential. We predict the signature of the gapped mode in lattice modulation experiments and show how it evolves with increasing interaction strength.
authors: Theoretische Physik, ETH Zurich, CH-8093 Zurich, Switzerland.
authors: S D
authors: SD
authors: Huber
authors: B
authors: B
authors: Theiler
authors: E
authors: E
authors: Altman
authors: G
authors: G
authors: Blatter