High-frequency nonlinear response of thin superconducting films with a mixed d and s symmetry of the order parameter

摘要

Third-harmonic generation during reflection of electromagnetic radiation from a thin superconducting film with a mixed d- and s-order parameter is studied theoretically. The dependence of the third harmonic intensity on the temperature and amplitude of an incident wave is calculated in the framework of the Ginzburg-Landau theory for superconductors with a two-component order parameter, and its behavior in the vicinity of transitions between phases with different symmetries is analyzed. It is shown, in particular, that the third harmonic intensity in the vicinity of the temperature corresponding to the d reversible arrow d + s phase transition substantially increases and is a nonanalytic function of the amplitude of the incident wave, while no singularity in the nonlinear response is observed for the d reversible arrow d + is transition. The linear reflection coefficient is found to be virtually insensitive to these phase transitions. (C) 2005 Pleiades Publishing, Inc.