Abstract
The concept of parity-time (PT) symmetry in SPPs is proposed and confirmed for the first time in this work. By introducing periodic modulation of the effective refractive index in SPP system, the asymmetric propagation is theoretically predicted and numerically demonstrated. After validation of this concept, we apply it in two applications: PT-waveguide and PT-cloak. Both two applications further illustrate the wide applicability of this concept in SPP system.