Low‐frequency excess noise in YBCO thin films near the transition temperature

We conducted detailed systematic studies on the properties of low frequency noise in YBCO thin films near the transition region. Detailed studies on the dependences of the low frequency noise on the biasing current, ∂R/∂T, and spatial correlation were conducted. It was shown that the measured voltage noise power spectra were proportional to I2 and (∂R/∂T)2, and were correlated over a spatial separation of 300 μm. Also, the voltage noise power spectral densities exhibit a lower cutoff frequency of 5 Hz, in excellent quantitative agreement with the cutoff frequency predicted by the Thermal Fluctuation model. The experimental results provide strong evidence that the low frequency excess noise in the device originated from equilibrium temperature fluctuations.