Wave tunneling through parity-time-symmetric epsilon-near-zero bi-layers

We study epsilon-near-zero (ENZ) bi-layers characterized by balanced loss and gain with parity-time (PT) symmetry, under oblique, transversely-magnetic-polarized plane-wave illumination. We show that total transmission (with zero reflection) may occur, mediated by the excitation of a surface-wave localized at the gain-loss interface, even in the presence of low levels of losses and gain. This constitutes an interesting example of a tunneling phenomenon induced by PT symmetry. Overall, the combination of the ENZ and PT-symmetry concepts may provide new perspectives in the introduction of gain and loss in metamaterials, and may lead to new waveguiding and radiation phenomena.