▎ 摘　　要

We report theoretical investigations that unveil unique electronic excitations in graphene nanoribbons of nanoscale length. The main point is that electronic states in short nanowires are standing particle-in-a-box-like waves, amenable to excitation by electromagnetic radiation. The unusual electronic and magnetic properties of graphene nanoribbons add another feature: terahertz (THz) radiation induces edge standing spin waves with different wavelengths at the two edges and a resonant frequency that can be controlled by an external gate voltage, opening the possibility of THz-spintronic applications.