Spawning Rings of Exceptional Points out of Dirac Cones

The Dirac point is a unique physical phenomenon that has been widely studied across different fields of physics: particle physics, condensed matter physics, etc. The Dirac point also underlies many unique physical properties of graphene and topological insulators. IRG I researchers have experimentally demonstrated that a ring of exceptional points can be spawned from a single Dirac point.

Exceptional points are unique non-Hermitian degeneracies with exotic properties. They have shown fascinating phenomena such as loss induced transparency, unidirectional transmission, etc. In this work, a non-Hermiticity was introduced by using radiation losses in a photonic crystal slab. By measuring the reflection, the band structure was recovered and demonstrated that a single Dirac point can give rise to a ring of exceptional points, called an “exceptional ring”.

This work bridges the fields of Dirac physics and non-Hermitian physics and can provide better understandings of the topological properties of exceptional points. From the application point of view, this work may lead to high-power lasers and better biological and chemical sensors.

Zhen, B., Hsu, C.W., Igarashi, Y., Lu, L., Kaminer, I., Pick, A., Chua, S.L., Joannopoulos, J.D., and Soljačić, M., Nature 524, 354, 14889 (2015).