Topological transition in coated wire medium
  We develop a theory of nonlocal homogenization for metamaterial consisting of parallel metallic wires with dielectric coating. It is demonstrated that manipulation of dielectric contrast between wire dielectric shell and host material results in switching of metamaterial dispersion regime from elliptic to the hyperbolic one, i.e. the topological transition takes place. We confirm our theoretical predictions by full-wave numerical simulations. 
Maxim A. Gorlach, Mingzhao Song, Alexey P. Slobozhanyuk, Andrey A.   Bogdanov and Pavel A. Belov
physics.optics cond-mat.mes-hall cond-mat.mtrl-sci