DETECTION OF ANDREEV REFLECTION CONTRIBUTION TO NONLINEAR IVC RESPONSE OF HTSC-NORMAL METAL POINT CONTACTS TO EXTERNAL MICROWAVE-RADIATION

Measurements of the I-V characteristics of S-c-N Nb-TlBaCaCuO point contacts have been performed over the temperature range 4,2 K to 300 K under applied microwave radiation at a frequency of about 12 GHz. Two types of the excess current dependence on the power P of the external radiation were found. In one case excess current oscillates with P increase that is explained by the processes of Andreev reflection in S-c-N contacts. In the other case the excess current is found to be stimulated by the radiation power. Obtained resultes indicate the presence of complicated picture of the quasi-particles dynamics in HTSC. The mechanisms of the nonlinear effects revealed are disscused.