Localized modes in the layered superconductor samples

Abstract

Subject and purpose. In this review the propagation of electromagnetic waves localized near the boundary of a sample of a layered superconductor with layers either parallel or perpendicular to its surface is discussed. The results obtained in a number of papers studying the dispersion law for such waves are generalized, classified and supplemented. Due to the strong anisotropy and nonlinearity of the Josephson plasma in layered superconductors, localized waves can have unusual dispersion properties, and their excitation can be accompanied by unusual resonance phenomena. Methods and methodology. The electromagnetic field in a layered superconductor is determined by the distribution of the gauge-invariant phase difference of the order parameter, which satisfies the system of coupled sin-Gordon equations. Based on the solution of these equations, as well as the Maxwell equations in the dielectric environment, dispersion relations can be obtained for localized electromagnetic modes. Results. In samples of a layered superconductor, whose layers are parallel to its boundary, both surface waves and waveguide modes with normal dispersion can propagate. For samples, the layers in which are perpendicular to the boundary, the dispersion law depends on the angle of propagation of the waves relative to the superconducting layers. In this paper it is shown for the first time that waves localized in a layered superconductor plate have an anomalous dispersion for all directions of propagation, except propagation strictly along the layers. Dispersion curves for such waves can have points of maximum and/or minimum, which can lead to nontrivial effects (e.g., stopping of light or internal reflection). Also, the excitation of localized waves and the unusual resonant phenomena are discussed in the work. Conclusions. Due to the strong anisotropy and nonlinearity of the layered superconductor, the dispersion laws for waves, localized both in semi-infinite samples and in plates have a number of interesting features that lead to new phenomena important for using in the physics of the terahertz range.

Keywords

• anomalous dispersion
• layered superconductor
• localized waves