The Amplitude Mode in the Quantum Phase Model
arXiv:0709.4436 · doi:10.1103/PhysRevLett.100.050404
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.
4 pages, 3 figures