Dynamical Chiral Symmetry and Symmetry-Class Conversion in Floquet Topological Insulators
Physical Review B(2024)
摘要
In this work, we discuss properties with no static counterpart arising in
Floquet topological insulators with a dynamical chiral symmetry (DCS), i.e., a
chiral symmetry which is present while driving. We explore the topological
properties of Floquet insulators possessing a DCS which either does or does not
survive upon taking the static limit. We consider the case of harmonic drives
and employ a general framework using the quasi-energy operator in frequency
space. We find that for a DCS with no static analog, the presence of driving
has a negligible impact on the topological phases associated with zero
quasi-energy. In stark contrast, topological gaps can open at π
quasi-energy and mainly occur at momenta where the driving perturbation
vanishes. We confirm the above general predictions for an extended Kitaev chain
model in the BDI symmetry class. Another possibility that opens up when adding
the drive, while preserving chiral symmetry, is symmetry-class conversion. We
demonstrate such an effect for a static CI class Hamiltonian which is
topologically trivial in 1D. By considering a suitable driving, we obtain a
CI→AIII transition, which now enables the system to harbor
topological π-modes. Notably, the arising topological phases strongly
depend on whether the DCS has a static analog or not. Our results bring Floquet
insulators with nonstandard DCS forward as ideal candidate platforms for
engineering and manipulating topological π-modes.
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