On a new type of massless Dirac fermions in crystalline topological insulators

• Published in: JETP letters 2013-11, Vol.98 (5), p.298-303
• Main Authors: Molotkov, S. N., Potapova, T. A.
• Format: Article
• Language: English
• Subjects: Atomic; Biological and Medical Physics; Biophysics; Methods of Theoretical Physics; Molecular; Optical and Plasma Physics; Particle and Nuclear Physics; Physics; Physics and Astronomy; Quantum Information Technology; Solid State Physics; Spintronics
• ISSN: 0021-3640; 1090-6487
• DOI: 10.1134/S0021364013180082

A new type of massless Dirac fermions in crystalline three-dimensional topological insulators (three-dimensional → two-dimensional situation) has been predicted. The spectrum has fourfold degeneracy at the top of the two-dimensional Brillouin zone (M point) and twofold degeneracy near the M point. Crystal symmetry along with the time reversal invariance in three-dimensional topological insulators allows fourfold degenerate Dirac cones, which are absent in the classification of topological features in R.-J. Slager et al., Nat. Phys. 9 , 98 (2013). The Hamiltonian in the cited work does not contain Dirac singularities with more than twofold degeneracy. For this reason, the corresponding topological classification is incomplete. The longitudinal magnetic field in the spinless case holds the massless dispersion law of fermions and does not lift fourfold degeneracy. In the spinor case, the magnetic field lifts fourfold degeneracy, holding only twofold degeneracy, and results in the appearance of a band gap in the spectrum of fermions.