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Granular superconductor in a honeycomb lattice as a realization of bosonic Dirac material
KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology. KTH, Centres, Nordic Institute for Theoretical Physics NORDITA. Institute for Materials Science, Los Alamos National Laboratory, USA.
KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.ORCID iD: 0000-0002-1763-9383
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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
American Physical Society , 2016. Vol. 93, no 13, 134502
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Theoretical Chemistry Physical Sciences
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URN: urn:nbn:se:kth:diva-185977DOI: 10.1103/PhysRevB.93.134502ISI: 000373566000006ScopusID: 2-s2.0-84963616046OAI: oai:DiVA.org:kth-185977DiVA: diva2:926167
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QC 20160504

Available from: 2016-05-04 Created: 2016-04-29 Last updated: 2016-05-12Bibliographically approved

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Banerjee, S.Ågren, Hans
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