Multiple higher-order topological phases with even and odd pairs of zero-energy corner modes in a C3symmetry broken model

Here we study emergent higher-order topological (HOTI) phases in the extended Haldane model without C3 symmetry. For the inversion symmetric case, the QSHI and QAHI phases can embed the HOTI phases while the remaining QASHI phase does not yield any HOTI phases. Remarkably, four-fold degeneracy of ze...

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Bibliographic Details
Published in:Europhysics letters 2023-06, Vol.142 (5), p.56002
Main Authors: Saha, Sudarshan, Nag, Tanay, Mandal, Saptarshi
Format: Article
Language:English
Subjects:
Lattice vibration
Phases
Symmetry
Topological insulators
Online Access:Get full text
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Summary:Here we study emergent higher-order topological (HOTI) phases in the extended Haldane model without C3 symmetry. For the inversion symmetric case, the QSHI and QAHI phases can embed the HOTI phases while the remaining QASHI phase does not yield any HOTI phases. Remarkably, four-fold degeneracy of zero-energy corner states can be reduced to two-fold under the application (withdrawal) of sub-lattice mass (Zeeman field) term. The sub-lattice mass and Zeeman field terms compete with each other to pin down the two mid-gap states at zero-energy. Interestingly, the bulk polarization can topologically characterize the second-order topological insulator phase with the mid-gap corner modes irrespective of their energies as long as inversion symmetry is preserved. Our study indicates that a hybrid symmetry can in principle protect the second-order topological insulator phases, however, spin-spectrum gap has to be essentially finite there.
ISSN:0295-5075
1286-4854
DOI:10.1209/0295-5075/acd71a