At EIT transmission peak, the induced surface current of six
SRRs and the cut wire are in opposite direction. However,
the induced surface currents along the cut wire are obviously
stronger than the induced surface currents around six SRRs.
Due to the strong surface currents of the cut wire, the coupling
strength of the whole EIT structure to incident electromagnetic
wave is higher compared with previously reported
EIT structure.41,42 Hence, a wide EIT transmission window
is generated. Fig. 4 depicts surface currents distributions of
the EIT structure at transmission dips and peak. At one transmission
dip (5.84 GHz), the surface currents are concentrated
around six SRRs and one cut wire. The currents along the
cut wire are generated by induced electric field of the six
SRRs, since the cut wire cannot be directly excited by the
incident electromagnetic wave. At another transmission dip
(6.86 GHz), nearly all the surface currents are distributed
along the cut wire. For the transmission peak (6.32 GHz), the
direction of the surface currents on six SRRs and one cut
wire is opposite. Due to the reversed current oscillations, the
induced electromagnetic fields on SRRs and cut wire are
canceled with each other, which result in high transmission
level.