Oblique surface Josephson plasma waves in layered superconductors

TL;DR

This paper theoretically investigates oblique surface Josephson plasma waves in layered superconductors, deriving their dispersion relations and analyzing their resonance excitation, revealing polarization transformation phenomena unique to anisotropic superconducting interfaces.

Contribution

It provides a novel theoretical analysis of oblique surface waves in layered superconductors, including dispersion equations and resonance excitation mechanisms considering anisotropy.

Findings

Dispersion curves have end-points where modes transform from evanescent to bulk waves.

Resonance excitation can induce polarization conversion even without dissipation.

Complete wave transformation into orthogonal polarization is possible under optimal conditions.

Abstract

We have theoretically studied oblique surface waves (OSWs) which propagate along the interface between a dielectric and a layered superconductor. We assume that this interface is perpendicular to the superconducting layers, and OSWs at the interface can propagate at an arbitrary angle with respect to them. The electromagnetic field of the OSWs in a layered superconductor is a superposition of an ordinary wave (with its electric field parallel to the layers) and an extraordinary wave (with its magnetic field parallel to the layers). We have derived the dispersion equation for the OSWs and shown that the dispersion curves have end-points where the extraordinary mode transforms from evanescent wave to bulk wave, propagating deep into the superconductor. In addition, we have analytically solved the problem of the resonance excitation of the OSWs by the attenuated-total-reflection method using an additional dielectric prism. Due to the strong current anisotropy in the boundary of the superconductor, the excitation of the OSWs is accompanied by an additional important phenomenon: the electromagnetic field component with the orthogonal polarization appears in the wave reflected from the bottom of the prism. We show that, for definite optimal combinations of the problem parameters (the wave frequency, the direction of the incident wave vector, the thickness of the gap between dielectric prism and superconductor, etc.), there is a complete suppression of the reflected wave with its polarization coinciding with the polarization of the incident wave. Contrary to the isotropic case, this phenomenon can be observed even in the dissipationless limit. In such a regime, the complete transformation of the incident wave into a reflected wave with orthogonal polarization can be observed.