Effects of microwave radiation on the noise in high- Tc YBa 2Cu 3O 7 dc SQUID magnetometer

Abstract

With a properly fabricated low-noise SQUID, we have studied the effects of microwave radiation on the noise behavior. Under an ac bias, with increasing microwave power, the critical current and the voltage modulation depth Δ V= Φ 0 V Φ /π decrease, but the SQUID resistance R s increases, suggesting a dynamical interaction between the charge carriers and the electromagnetic wave. Furthermore, the microwave radiation modifies drastically the functional dependence of S Φ and Δ V on ac bias current.