Congratulations to Yang Wu, Dongfanghao and Yunhan Wang for publishing  Experimental Observation of Dirac Exceptional Points on Physical Review Letters as “Editors’ Suggestion”!

The energy level degeneracies, also known as exceptional points (EPs), play a fundamental role in understanding emergent phenomena in materials and novel functionalities for devices. Since EPs have been proposed over half a century ago, only two types of EPs have been experimentally discovered, revealing intriguing phases of materials such as Dirac/Weyl semimetals, numerous exotic topological properties and novel applications such as unidirectional energy transfer. In this work, we experimental observe a new type of EP, named as Dirac EP utilizing a nitrogen-vacancy center in diamond. In the vicinity of the Dirac EP, the eigenvalues observed to be real, exhibiting contrast with typical EPs’ behavior. The measured degeneracy of the eigenstates further confirms that the Dirac EP is entirely different from Hermitian degeneracy. The exotic band topology associated with this type of EP not only unveils an unprecedented mechanism for dynamics in non-Hermitian systems, but also provides the possibility of achieving adiabatic evolution in non-Hermitian systems. The Dirac EP discovered in this work could potentially generate broad interests in new properties of materials while simultaneously unlock pathways of applications in photonic, phononic, mechanical and quantum systems.

 

https://doi.org/10.1103/PhysRevLett.134.153601