Transport and noise in YBa2Cu307 ramp junctions and 2-dimensional quantum interference filters

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Ramp-type Josephson junctions made of the high-transition temperature (high-Tc) cuprate superconductor YBa2Cu3O7 (YBCO), with controlled interface and barrier properties shall be realized with improved fabrication techniques, including an in-situ process for the involved interfaces. Using high-quality YBCO ramp junctions, we want to achieve two goals: (i) Systematic experimental studies of electric transport and noise, combined with spatially resolved analysis by low-temperature scanning electron microscopy (LTSEM), and theoretical modeling based on the quasi-classical Eilenberger equations, shall provide an understanding of the transport processes across ramp-type junctions of a d-wave superconductor, with tailored interfaces and barriers. (ii) Two-dimensional (2D) superconducting quantum interference filters (SQIFs) shall be realized and investigated. SQIFs are Josephson junction interferometers, designed as irregular arrangements of superconducting loops according to specific statistical distributions. Such junction networks can be tailored to show a characteristic response for magnetic fields, which allows to measure absolute magnetic fields with extremely high sensitivity, linearity and dynamic range. 2D YBCO SQIFs are particularly appealing for applications in single-stage cryocoolers above 60 K. Besides the detection of static and low-frequency magnetic fields, such SQIFs can be designed as extremely wide-band sensors, preamplifiers and mixers for electromagnetic signals (long wave up to satellite frequencies in the Ka band). This opens new perspectives for the application of superconducting electronics in communication technology.