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Flat bands and Z2 topological phases in a non-Abelian kagome lattice

Gao, Z; Lan, Z; (2020) Flat bands and Z2 topological phases in a non-Abelian kagome lattice. Physical Review B , 102 (24) , Article 245133. 10.1103/physrevb.102.245133. Green open access

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Abstract

We introduce a non-Abelian kagome lattice model that has both time-reversal and inversion symmetries and study the flat band physics and topological phases of this model. Due to the coexistence of both time-reversal and inversion symmetries, the energy bands consist of three doubly degenerate bands whose energy and conditions for the presence of flat bands could be obtained analytically, allowing us to tune the flat band with respect to the other two dispersive bands from the top to the middle and then to the bottom of the three bands. We further study the gapped phases of the model and show that they belong to the same phase as the band gaps only close at discrete points of the parameter space, making any two gapped phases adiabatically connected to each other without closing the band gap. Using the Pfaffian approach based on the time-reversal symmetry and parity characterization from the inversion symmetry, we calculate the bulk topological invariants and demonstrate that the unique gapped phases belong to the Z2 quantum spin Hall phase, which is further confirmed by the edge state calculations

Type: Article
Title: Flat bands and Z2 topological phases in a non-Abelian kagome lattice
Open access status: An open access version is available from UCL Discovery
DOI: 10.1103/physrevb.102.245133
Publisher version: https://doi.org/10.1103/physrevb.102.245133
Language: English
Additional information: This version is the version of record. For information on re-use, please refer to the publisher’s terms and conditions.
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Electronic and Electrical Eng
URI: https://discovery.ucl.ac.uk/id/eprint/10118629
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