Exceptional point in tunable terahertz metasurface based on bulk Dirac semimetal

In this study, we designed a tunable metasurface using bulk Dirac semimetal, whose periodic unit consisted of two orthogonally oriented split rings with identical dimensions in resonator mode, to observe and study exceptional points (EPs). By changing the Fermi level of the Dirac semimetal, the PT symmetry phase transitioned to the PT symmetry-breaking phase, which enabled the observation of an EP. The proposed method exploits the sensitivity of EPs to the perturbations in the system. The results calculated using the coupled mode theory were consistent with the results of simulations and have significant implications in polarization detection, manipulation, and ultrasensitive sensing.