▎ 摘　　要

We use a two-dimensional two-component nonlinear hydrodynamic method to study valley-dependent plasmons in bounded strained graphene in the presence of an irradiating proton, realizing electrostatic control of the valley-dependent plasmons in actual space. We use flux-corrected transport to solve the nonlinear hydrodynamic equations numerically and self-consistently. Our results answer the important question of whether full valley polarization can be obtained in a specific valley at the boundary or inside the graphene sheet in the presence of the injected proton. The electrons experience collective excitations due to the proton interaction and the strain-induced pseudomagnetic field. The electron density fluctuation can be much larger than the equilibrium electron density, leading to a strong nonlinear effect and thus full valley polarization. This demonstrates the nature of the nonlinear response of electrons in graphene to strong interactions, a response that originates from the strong nonperturbative interaction between the irradiating proton and the electrons. Thus, our method opens up the possibility of investigating the nonlinear behavior of valley-dependent plasmons in strong modulations. The effects of the proton on the valley polarization are examined. There is K-polarization inside the surface behind the proton, whereas there is K'-polarization at the edge which decays away from the edge, thereby switching the valley polarization. This work establishes a link between actual-space valley-dependent plasmons in graphene and the irradiating proton and provides an alternative way to realize full valley polarization with tunable polarity. Compared to the case with no proton, the valley polarization is enhanced considerably in the presence of a proton. Published under license by AIP Publishing.