Lattice generalization of the Dirac equation to general spin and the role of the flat band

Balázs Dóra, Janik Kailasvuori, and R. Moessner
Phys. Rev. B 84, 195422 – Published 7 November 2011

Abstract

We provide a setup for generalizing the two-dimensional pseudospin S=1/2 Dirac equation, arising in graphene’s honeycomb lattice, to general pseudospin S. We engineer these band structures as a nearest-neighbor hopping Hamiltonian involving stacked triangular lattices. We obtain multilayered low-energy excitations around half-filling described by a two-dimensional Dirac equation of the form H=vFS·p, where S represents an arbitrary spin S (integer or half-integer). For integer S, a flat band appears, the presence of which modifies qualitatively the response of the system. Among physical observables, the density of states, the optical conductivity, and the peculiarities of Klein tunneling are investigated. We also study Chern numbers as well as the zero-energy Landau-level degeneracy. By changing the stacking pattern, the topological properties are altered significantly, with no obvious analog in multilayer graphene stacks.

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  • Received 14 April 2011

DOI:https://doi.org/10.1103/PhysRevB.84.195422

©2011 American Physical Society

Authors & Affiliations

Balázs Dóra1,*, Janik Kailasvuori2,3, and R. Moessner2

  • 1Department of Physics, Budapest University of Technology and Economics, Budafoki út 8, HU-1111 Budapest, Hungary
  • 2Max-Planck-Institut für Physik komplexer Systeme, Nöthnitzer Str. 38, DE-01187 Dresden, Germany
  • 3International Institute of Physics, Universidade Federal do Rio Grande do Norte, 59078-400 Natal-RN, Brazil

  • *dora@pks.mpg.de

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Issue

Vol. 84, Iss. 19 — 15 November 2011

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