  Microplasma generation using microwaves in an electromagnetically induced
transparency (EIT)-like metasurface composed of two types of radiatively
coupled cut-wire resonators with slightly different resonance frequencies is
investigated. Microplasma is generated in either of the gaps of the cut-wire
resonators as a result of strong enhancement of the local electric field
associated with resonance and slow microwave effect. The threshold microwave
power for plasma ignition is found to reach a minimum at the EIT-like
transmission peak frequency, where the group index is maximized. A pump-probe
measurement of the metasurface reveals that the transmission properties can be
significantly varied by varying the properties of the generated microplasma
near the EIT-like transmission peak frequency and the resonance frequency. The
electron density of the microplasma is roughly estimated to be of order
$1\times 10^{10}\,\mathrm{cm}^{-3}$ for a pump power of $15.8\,\mathrm{W}$ by
comparing the measured transmission spectrum for the probe wave with the
numerically calculated spectrum. In the calculation, we assumed that the plasma
is uniformly generated in the resonator gap, that the electron temperature is
$2\,\mathrm{eV}$, and that the elastic scattering cross section is $20 \times
10^{-16}\,\mathrm{cm}^2$.
