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Metamaterial based electromagnetically induced transparency (EIT) analogue have attracted as an alternative way to realize exotic EIT applications such as slow light devices and biosensors. Researches on metamaterial EIT analogues have recently focused on the realization of active system to control the EIT-like spectral properties via various external stimuli, including optical, mechanical, and thermal methods. Graphene based EIT metamaterials have been also reported through the numerical analysis as an electrically controlled active system, but there are no experimental reports in terahertz regime due to insufficient electrical mobility and conductance variation range of practical graphene sheets to realize active EIT analogues. In our previous study, we had reported a new concept of metamaterial analogue to achieve EIT-like phenomena, in which cut-wire (CW) pair and pseudo complementary cut-wire (CCW) were orthogonally combined with each other, generating EIT-like properties by funneling terahertz waves through the pseudo-CCW hole in broad reflection resonance of CW pair. Since this extraordinary transmission could be easily suppressed with resistive conductors along the pseudo-CCW structure, we designed the ion-gel gated graphene lines on the center of meta-atom structures to control the funneling of terahertz waves. Controlling the electromagnetic funneling provided switchable EIT-like spectral properties of the proposed metamaterials and we numerically confirmed that the graphene lines successfully acted as switching materials, even if the lines were formed with practically achievable graphene films. Finally, we verified that the fabricated EIT metamaterials experimentally showed 54.9% of modulation depth and 1ps of group delay change at the transmission peak in terahertz range.
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