| A basic assumption of quantum mechanics is that the operator of observable physical quantity in the quantum system must be the Hermite operator.Not only is the eigenvalue of Hermite operator a real number,but is has been found that the non-Hermite Hamiltonian with parity-time symmetry can also have real spectra.As we all know there are so-called exceptional point in non-Hermitian systems,and many extraordinary physical properties can be generated at exceptional point,such as unidirectional reflectionlessness,perfect absorption,loss-induced transparency,quantum phase transition and so on.The study on unidirectional reflectionless-ness and perfect absorption has important significance in filters,sensors,anisotropic nanodevices and so on.Since surface plasmon or photon was considered as ideal carriers of quantum information,in recent years,an important topic for the transport properties of single surface plasmon or photon in one dimensional(1D)waveguide was investigated by many researchers in Hermitian and non-Hermitian systems.So far,most of the research has focused on the transmission characteristics of a non-Hermitian system in which a single plasmon interacting with a quantum dot in an optical waveguide or a metal nanowire.However,the study on the propagation properties of surface plasmon in the non-Hermitian quantum dot-plasmonic waveguide coupling system is rarely mentioned.Therefore,we propose a method to realize the non-reciprocal scattering properties in a non-Hermitian quantum system of quantum dot-surface plasmonic waveguide.In this paper,unidirectional reflectionless phenomena in a non-Hermitian quan-tum system of quantum dots coupled to a plasmonic waveguide based on the phase coupling of quantum dots.We respectively realize the single-and dual-band u-nidirectional reflectionlessnesses by adjusting the phase coupling of two and three quantum dots.In addition,we discuss the quality factors of single-and dual-band unidirectional reflectionlessness and coherent perfect absorptions.Not only that our scheme can be extended to realize the n-1 bands unidirectional reflectionlessness in non-Hermitian system based on the coupling of n quantum dots. |
