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Granular superconductor in a honeycomb lattice as a realization of bosonic Dirac material
Los Alamos Natl Lab, Inst Mat Sci, Los Alamos, NM 87545 USA.;KTH Royal Inst Technol, Ctr Quantum Mat, Nordita, Roslagstullsbacken 23, S-10691 Stockholm, Sweden.;Stockholm Univ, Roslagstullsbacken 23, S-10691 Stockholm, Sweden.;Royal Inst Technol, Div Theoret Chem & Biol, SE-10691 Stockholm, Sweden..
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
Royal Inst Technol, Div Theoret Chem & Biol, SE-10691 Stockholm, Sweden..
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2016 (English)In: PHYSICAL REVIEW B, ISSN 2469-9950, Vol. 93, no 13, 134502Article in journal (Refereed) PublishedText
Abstract [en]

We examine the low-energy effective theory of phase oscillations in a two-dimensional granular superconducting sheet where the grains are arranged in a honeycomb lattice structure. Using the example of graphene, we present evidence for the engineered Dirac nodes in the bosonic excitations: the spectra of the collective bosonic modes cross at the K and K' points in the Brillouin zone and form Dirac nodes. We show how two different types of collective phase oscillations are obtained and that they are analogous to the Leggett and the Bogoliubov-Anderson-Gorkov modes in a two-band superconductor. We show that the Dirac node is preserved in the presence of an intergrain interaction, despite induced changes of the qualitative features of the two collective modes. Finally, breaking the sublattice symmetry by choosing different on-site potentials for the two sublattices leads to a gap opening near the Dirac node, in analogy with fermionic Dirac materials. The Dirac node dispersion of bosonic excitations is thus expanding the discussion of the conventional Dirac cone excitations to the case of bosons. We call this case as a representative of bosonic Dirac materials (BDM), similar to the case of Fermionic Dirac materials extensively discussed in the literature.

Place, publisher, year, edition, pages
2016. Vol. 93, no 13, 134502
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:uu:diva-294672DOI: 10.1103/PhysRevB.93.134502ISI: 000373566000006OAI: oai:DiVA.org:uu-294672DiVA: diva2:932299
Funder
Knut and Alice Wallenberg Foundation, KAW-2013.0020EU, European Research Council, DM-321031Swedish Research Council
Available from: 2016-06-01 Created: 2016-05-26 Last updated: 2016-06-01Bibliographically approved

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Fransson, JonasBlack-Schaffer, Annica M.
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