Switchable Hyperbolic Metamaterials With Magnetic Control
  A switchable hyperbolic material (SHM) is investigated, with which one can turn on or off the hyperbolic dispersion of the material via magnetic control. The SHM has simple structure, with a one-dimensional periodic stacking of dielectric layer and gyromagnetic layer. The hyperbolic dispersion of SHM is due to the negative effective permeability of gyromagnetic layers, and it can be transformed into a regular circular dispersion when the d.c. magnetic field is switched off. This switchable dispersion transition is reversible, which may have great potential applications in many fields. 
Wei Li, Zheng Liu, Xiaogang Zhang, and Xunya Jiang
physics.optics