Zero-refraction in natural materials and the mechanism of metal   superlens
  We found that a single negative material has a character of zero-refraction in near field, and point out that the mechanism of a metal superlens to image with the resolution exceeding the diffraction limitation is different from that of a perfect lens made of a double negative material. The principle of metal superlens is disclosed. Our numerical results based on the zero-refraction character coincide with the experimental results well. This work brings new understanding about the single negative materials and will lead the applications of metal superlens in right way. 
Yun-Song Zhou (1), Huai-Yu Wang (2), Hai Wang (1) ((1) Center of   Theoretical Physics, Department of Physics, Capital Norma...
physics.optics