Quantum-Field Laser Laboratory, KW An's Group

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05 Seminars

Exceptional points in coupled microdisks

Jung-Wan Ryu

IBS Center for Theoretical Physics of Complex Systems

IBS Center for Theoretical Physics of Complex Systems

We investigate the exceptional point (EP) in coupled microdisks. A microdisk is an open system in the sense that the ray with the incident angle smaller than the critical angle refractively escapes from the cavity. Energy levels of open quantum systems have several distinct properties compared with those of closed ones; first of all the system is described as non-Hermitian Hamiltonian, so that the eigenvalues are complex and the eigenstates form a nonorthogonal set. In particular, the behavior of two interacting energy levels as varying external parameters are mainly governed by the so-called EP, where the complex eigenvalues of the corresponding levels coalesce, i.e., forming the degeneracy of complex eigenvalues. The EP has some noticeable characteristics such as nontrivial topology around the EP in a parameter space. To observe it, at least two independent external parameters are necessary. We find that the coupled microdisks provides an ideal system to investigate the properties of EPs. In the coupled microdisks, two control parameters naturally exist; namely, the distance between two disks and the ratio between two radii, which allows us to explore the EP. We obtain many EPs in coupled microdisks and discuss their interesting characteristics.

Last updated: April 14, 2016