▎ 摘　　要

We show that the magnetization of triangular graphene quantum dots with zigzag edges can be manipulated optically. When the system is charge neutral, the magnetic moment can be first erased by addition of a single electron spin with a gate, then restored by absorption of a photon. The conversion of a single photon to a magnetic moment results in a many-body effect, optical spin blockade. The effect demonstrated here can potentially lead to efficient spin to photon conversion, quantum memories, and single-photon detectors. DOI: 10.1103/PhysRevB.87.035425