  Non-Hermiticity has recently emerged as a rapidly developing field due to its
exotic characteristics related to open systems, where the dissipation plays a
critical role. In the presence of balanced energy gain and loss with
environment, the system exhibits parity-time (PT) symmetry, meanwhile as the
conjugate counterpart, anti-PT symmetry can be achieved with dissipative
coupling within the system. Here, we demonstrate the coherence of complex
dissipative coupling can control the transition between PT and anti-PT symmetry
in an electromagnetic metamaterial. Notably, the achievement of the anti-PT
symmetric phase is independent of variations in dissipation. Furthermore, we
observe phase transitions as the system crosses exceptional points in both
anti-PT and PT symmetric metamaterial configurations, achieved by manipulating
the frequency and dissipation of resonators. This work provides a promising
metamaterial design for broader exploration of non-Hermitian physics and
practical application with controllable Hamiltonian.
