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" (${\omega }_1, {\omega }_s$). The limiting frequencies are defined by ${\epsilon }_1\left({\omega }_1\right)=0\mathrm{}$ and ${\epsilon }_1\left({\omega }_s\right)+{\epsilon }_2\left({\omega }_s\right)=0\mathrm{}$, where ${\epsilon }_i\left(\omega \right)$, $i=1, 2$, are the dielectric functions of the two media. If the Drude approximation for ${\epsilon }_i\left(\omega \right)$ is applicable then ${{\omega }_s}^2=\frac{({\epsilon }_{L1\mathrm{}}{\omega }_1^2+{\epsilon }_{L2\mathrm{}}{\omega }_2^2)}{({\epsilon }_{L1\mathrm{}}+{\epsilon }_{L2\mathrm{}})}$, where ${\omega }_i$ and ${\epsilon }_{\mathrm{Li}}$ 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.