Large group index induced by asymmetric split ring resonator dimer

In this manuscript, we experimentally and numerically demonstrate group delay enhancement of an asymmetric split ring resonators (SRRs) metamaterial dimer. By introducing minor different magnetic resonances between dimer SRRs, a sharp transmission peak located between two dips is observed, which is in analogy to classical electromagnetically induced transparency. Transmission phase of asymmetric SRR dimer experiences steep dispersion, resulting in an increase of group index to 150. Furthermore, the underlying physics can be explained by suppressed mode formed by opposite magnetic dipoles of asymmetric SRRs.