We experimentally demonstrate one-way transparency of light in multiferroic ${\mathrm{CuB}}_2{\mathrm{O}}_4$. The material is rendered transparent for light propagating in one direction, while opaque for light propagating in the opposite direction. The novel transparency results from a destructive interference of the electric dipole and magnetic dipole transitions. The realization of the effect has been accomplished by the application of a high magnetic field and the proper selection of the propagation direction of light in agreement with our quantum mechanical formulation of nonreciprocal directional dichroism.

• Received 23 September 2015

DOI:https://doi.org/10.1103/PhysRevLett.115.267207