Electromagnetic wave propagation at the interface between two conductors

We predict a new plasmon-polariton mode---supported by a biconducting interface in a certain frequency "window" (ω₁, ωₛ). The limiting frequencies are defined by ε₁(ω₁)=0 and ε₁(ωₛ)+ε₂(ωₛ)=0, where εᵢ(ω), $i=1, 2$, are the dielectric functions of the two media. If the Drude approximation for εᵢ(ω) is applicable then ${{{ω}}ₛ}²={({{ε}}L1{{ω}}₁²+{{ε}}L2{{ω}}₂²)}{({{ε}}L1+{{ε}}L2)}$, where ${{ω}}ᵢ$ and ${{ε}}Li$ are the plasma frequencies and lattice dielectric constants of the conductors. These "interface plasmons" may propagate at a metal-metal, or semiconductor-semiconductor, or metal-semiconductor interface. The dispersion, damping, and polarization of the modes are analyzed in the retardation region. Optical methods of excitation and detection are discussed.