Effect of junction critical current disorder in superconducting quantum interference filter arrays

In this study, we investigated the performance of two 2D superconducting\nquantum interference filter (SQIF) arrays fabricated from YBCO thin films at a\ntemperature of 77 K. Each array consisted of 6 Josephson junctions (JJs) in\nparallel and 167 in series. We conducted both experimental and theoretical\nanalyses, measuring the arrays' voltage responses to an applied magnetic field\nand their voltage versus bias-current characteristics. To properly model the\nplanar array layouts, our theoretical model used the stream function approach\nand also included the Johnson noise in the JJs. The model further divides the\nsuperconducting current density of the arrays into its Meissner current,\ncirculating current, and bias current parts for practicality. Since the\nfabrication process of YBCO thin films cannot produce identical JJ critical\ncurrents, we assumed a log-normal distribution to model the JJ critical current\ndisorder. Our model predictions, with a JJ critical current spread of 50%,\nagreed well with our experimental data. Using our model, we were able to study\nthe dependence of the voltage modulation depth on critical current disorder and\nLondon penetration depth. We also analyzed the observed reflection asymmetries\nof the voltage versus magnetic field characteristics, which might provide\ninsight into the degree of critical current disorder. Overall, our findings\nsuggest that the use of YBCO thin films in SQIF arrays is promising, despite\nthe critical current disorder inherent in their fabrication process. Our study\nhighlights the importance of theoretical modeling in understanding the\nperformance of superconducting devices and provides insights that could inform\nthe design of future SQIF arrays.\n