Polarization-insensitive classical electromagnetically induced transparency metamaterial with large group delay by Dirac semimetal

We studied the Classical electromagnetically induced transparency (Cl-EIT) of a non-centrosymmetric metamaterial structure based on Dirac semimetal films (DSFs), which is polarization-insensitive and tunable. It is composed of a square ring and two U-shaped rings. By analyzing the distribution and intensity of the current, we find that Cl-EIT is caused by destructive interference between the resonators that produce near-field coupling. As the Fermi level of DSFs increases, the transparent window of the Cl-EIT structure blueshifts and has a good linear relationship with the Fermi level. For DSFs with different Fermi levels, we calculated their transmission phases and group delays where the maximum group delay is 31.35 ps, and the delay-bandwidth product (DBP) at this point can reach 0.658. The proposed metamaterial structure opens up a new path for various terahertz applications, such as optical storage and slow-light devices.