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  • Letter
  • Open Access

Topological edge states of massless fermions with nonquantized and zero Berry phases

F. R. Pratama1,2,* and Takeshi Nakanishi1,†

  • *Contact author: pratama.fr@aist.go.jp
  • †Contact author: t.nakanishi@aist.go.jp

Phys. Rev. B 110, L161409 – Published 22 October, 2024

DOI: https://doi.org/10.1103/PhysRevB.110.L161409

Abstract

We investigate the bulk-boundary correspondence for massless Dirac fermions in α−T3 lattice where the Berry phase can be continuously tuned from π (graphene) to 0 (T3 or dice lattice) without modifying the energy dispersion. The topological origin of edge states is revealed by the unitary transformation of the Hamiltonian, which maps an α−T3 zigzag ribbon (ZR) onto a stub Su-Schrieffer-Heeger (SSH) chain. In the Majorana representation of the eigenstates, the topological invariant is manifested by the azimuthal winding number on the Bloch sphere. Particularly, T3 ZR exemplifies a topologically nontrivial system with zero Berry phase. Contrary to conventional topological insulators, the gap closing in the corresponding stub SSH chain is not accompanied by a topological phase transition.

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