J. Phys. III France
Volume 2, Numéro 3, March 1992
Page(s) 355 - 372
DOI: 10.1051/jp3:1992134
J. Phys. III France 2 (1992) 355-372

Nonlinear microwave response of a YBaCuO

M. R. Trunin1 and G. I. Leviev2

1  Bergische Universität Wuppertal, D-5600 Wuppertal 1, Germany
2  Institute of Solid State Physics, 142432 Chernogolovka, Moscow district, Russia

(Received 31 May 1991, revised 21 November 1991, accepted 25 November 1991)

The review of modern situation concerning the studies of the generation of microwave harmonics in YBaCuO is given. Far from $T_{\rm c}$ the nonlinear response of ceramics YBaCuO has Josephson nature in a weak magnetic fields or is described in terms of the critical state model in a strong external magnetic field H. Near $T_{\rm c}$, the signals of the second $P_{2\omega}(T)$ and the third $P_{3\omega}(T)$ harmonics have the form of spikes of generation. Yet the signal $P_{2\omega}(H)$ shows a hysteresis and is proportional to the square of incident power $P_{2\omega}\propto P^2_\omega$ while the signal $P_{3\omega}\propto P^3_\omega$ and doesn't depend on the field H. Such behavior of the nonlinear response near $T_{\rm c}$ is typical of both ceramics and single crystals of YBaCuO. We use the Portis model to describe the signal $P_{2\omega}$ and the model based on Eliashberg theory to describe the signal $P_{3\omega}$. The question about the model which can simultaneously explain the behavior of the second and the third harmonics remains open.

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