Suppressed\nNonreciprocal Second-Harmonic Generation\nof Antiferromagnet MnPSe<sub>3</sub> in the MnPSe<sub>3</sub>/Graphene\nHeterostructure Due to Interfacial Magnon–Plasmon Coupling

Interfacial coupling is one of the keys to manipulating\nmagnetic/nonmagnetic\ntwo-dimensional (2D) heterostructures for novel functionalities. The\nMnPSe<sub>3</sub>/graphene heterostructure is a prospective platform\nfor quantum information and metrology. However, how graphene affects\n MnPSe<sub>3</sub> through interfacial coupling is still poorly understood.\nHerein, second-harmonic generation (SHG) of antiferromagnet MnPSe<sub>3</sub> in the MnPSe<sub>3</sub>/graphene heterostructure is revealed.\nSurprisingly, it was found that below <i>T</i><sub>N</sub>, nonreciprocal or c-type SHG of MnPSe<sub>3</sub> disappeared when\ninterfacing with the graphene, suggesting the existence of interfacial\ncouplings and/or interactions. Most interestingly, different from\nthe short-range interfacial proximity interaction, this interfacial\ninteraction could be contactless and long-range and varied from 2D\nmetallic/semiconducting to insulating underlayers. Interfacial magnon–plasmon\ncoupling probably played an important role in suppressing the c-type\nSHG signals of MnPSe<sub>3</sub> in the MnPSe<sub>3</sub>/graphene\nheterostructure. This study will improve our understanding of the\nmanipulation of nonlinear optical properties in 2D heterostructures.