Abstract
We study a two-state non-Hermitian waveguide system that carries an exceptional point (EP). It is commonly believed that dynamically encircling an EP exhibits a chiral behavior when the starting point of the loop lies in the branch cut with eigenmodes being symmetric and antisymmetric modes. We show here that such statement is conditional; i.e., the dynamics can in fact be nonchiral for specially designed loops with the starting point in the branch cut. In particular, we find that for two homotopic loops (i.e., loops that can be transformed continuously from one to another without crossing any EP), the outcomes can be completely different even if the two loops share the same starting state, enclose the same EP, and encircle the EP in the same direction. Our findings greatly enrich the understanding of the physics in dynamical processes of EP encircling in non-Hermitian systems.
2 More- Received 11 March 2019
DOI:https://doi.org/10.1103/PhysRevA.99.063831
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