Flicker (1/<i>f</i>) noise in biepitaxial grain boundary junctions of YBa2Cu3O7−<i>x</i>

Abstract

At low frequencies f the 1/f noise power in single biepitaxial junctions of YBa2Cu3 O7−x peaks sharply for bias currents just above the noise reduced critical current and increases as I2 for high bias currents I. This behavior is explained by a model in which both critical current fluctuations δI0 and resistance fluctuations δR contribute to the measured voltage noise. The magnitude of the normalized critical-current fluctuations ‖δI0/I0‖ is always much greater than that of the normalized resistance fluctuations ‖δR/R‖. Switching the bias current between positive and negative values at 2 kHz greatly reduces the magnitude of the 1/f noise from both sources, implying that the coherence of the noise generating process is not affected by the current reversal.