Braids and Higher-order Exceptional Points from the Interplay Between
Lossy Defects and Topological Boundary States
- URL: http://arxiv.org/abs/2312.03054v1
- Date: Tue, 5 Dec 2023 19:00:00 GMT
- Title: Braids and Higher-order Exceptional Points from the Interplay Between
Lossy Defects and Topological Boundary States
- Authors: Zi-Jian Li, Gabriel Cardoso, Emil J. Bergholtz, Qing-Dong Jiang
- Abstract summary: We show that the perturbation of the Su-Schrieffer-Heeger chain by a localized lossy defect leads to higher-order exceptional points (HOEPs)
On the one hand, they arise due to the non-Abelian braiding properties of exceptional lines (ELs) in parameter space.
On the other hand, we show that such special intersections happen due to the fact that the delocalization of edge states, induced by the non-Hermitian defect, hybridizes them with defect states.
- Score: 2.157270652860098
- License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
- Abstract: We show that the perturbation of the Su-Schrieffer-Heeger chain by a
localized lossy defect leads to higher-order exceptional points (HOEPs).
Depending on the location of the defect, third- and fourth-order exceptional
points (EP3s & EP4s) appear in the space of Hamiltonian parameters. On the one
hand, they arise due to the non-Abelian braiding properties of exceptional
lines (ELs) in parameter space. Namely, the HOEPs lie at intersections of
mutually non-commuting ELs. On the other hand, we show that such special
intersections happen due to the fact that the delocalization of edge states,
induced by the non-Hermitian defect, hybridizes them with defect states. These
can then coalesce together into an EP3. When the defect lies at the midpoint of
the chain, a special symmetry of the full spectrum can lead to an EP4. In this
way, our model illustrates the emergence of interesting non-Abelian topological
properties in the multiband structure of non-Hermitian perturbations of
topological phases.
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