Investigation of the Bosonic Spectrum of Two-Dimensional Optical Graphene-Type Lattices. Superfluid Phase

  • I. V. Stasyuk Institute for Condensed Matter Physics, Nat. Acad. of Sci. of Ukraine
  • O. V. Velychko Institute for Condensed Matter Physics, Nat. Acad. of Sci. of Ukraine
  • I. R. Dulepa Institute for Condensed Matter Physics, Nat. Acad. of Sci. of Ukraine
Keywords: optical lattice, honeycomb lattice, phase transition, spectral density, hard-core bosons, Dirac points

Abstract

The energy spectrum of a system of Bose atoms in the superfluid phase in an optical lattice of the graphene type has been studied. The dispersion laws for the energy bands and the single particle spectral densities are calculated in the random phase approximation and in the framework of the hard-core boson formalism, and their changes at the transition from the normal phase to the superfluid one are described. As a result of this transformation, the number of subbands doubles. In the case of the subband energetic equivalence, the Dirac points in the spectrum survive, and their number becomes twice as much. When the subbands are energetically nonequivalent, the Dirac points are absent. The shape of spectral densities is shown to be sensitive to the changes in the temperature and the chemical potential position.

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Published
2018-10-25
How to Cite
Stasyuk, I., Velychko, O., & Dulepa, I. (2018). Investigation of the Bosonic Spectrum of Two-Dimensional Optical Graphene-Type Lattices. Superfluid Phase. Ukrainian Journal of Physics, 59(10), 993. https://doi.org/10.15407/ujpe59.10.0993
Section
Solid matter