Experimental observation of optical Weyl points and Fermi arc-like surface states
Chong, Yi Dong
Chen, Kevin P.
Rechtsman, Mikael C.
Date of Issue2017
School of Physical and Mathematical Sciences
Centre for Disruptive Photonic Technologies
Weyl fermions are hypothetical two-component massless relativistic particles in three-dimensional (3D) space, proposed by Hermann Weyl in 1929. Their band-crossing points, called ‘Weyl points’, carry a topological charge and are therefore highly robust. There has been much excitement over recent observations of Weyl points in microwave photonic crystals and the semimetal TaAs. Here, we report on the experimental observation of ‘type-II’ Weyl points of light at optical frequencies, with the photons having a strictly positive group velocity along one spatial direction. We use a 3D structure consisting of laser-written waveguides, and show the presence of type-II Weyl points by observing conical diffraction along one axis when the frequency is tuned to the Weyl point; and observing the associated Fermi arc-like surface states. The realization of Weyl points at optical frequencies allows these novel electromagnetic modes to be further explored in the context of linear, nonlinear, and quantum optics.
© 2017 Macmillan Publishers Limited, part of Springer Nature. This is the author created version of a work that has been peer reviewed and accepted for publication by Nature Physics, Macmillan Publishers Limited, part of Springer Nature. It incorporates referee’s comments but changes resulting from the publishing process, such as copyediting, structural formatting, may not be reflected in this document. The published version is available at: [http://dx.doi.org/10.1038/nphys4072].