Quantum and Topological Plasmons in Two Dimensions

In this talk, I will first present our observation of quantum-spilling enhanced surface-plasmon absorption at the interface of silver and high-index dielectrics. We show that due to the reduced work function of the high-index dielectrics with respect to the Fermi surface of the metal, conduction electrons can have a significant quantum spilling into the dielectrics. This phenomenon allows for intense interfacial electron-hole pair production along with the surface-plasmon absorption at optical frequencies. The enhancement occurs in the favorable solar-spectrum regime, and so can be helpful for developing high-efficiency energy-harvesting devices. I will then present our recent studies on the topological behaviors of two-dimensional magneto plasmons in GaAs/AlGaAs hetero junctions and on monolayer graphene. We show that with a modest magnetic field to break the time-reversal symmetry, topologically protected one-way edge states can exist on both density-termination boundaries and magnetic-domain boundaries. These edge states are operable from gigahertz to terahertz frequencies and can potentially be used to develop low-loss high-speed electronic-photonic hybridized devices.