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

由高转变温度（高tc）铜超导体YBa2Cu3O7 （YBCO）制成的具有控制界面和势垒性质的斜坡型约瑟夫森结，需要通过改进的制造技术来实现，包括所涉及的界面的原位工艺。利用高质量的YBCO斜坡结，我们希望实现两个目标：(i)电输运和噪声的系统实验研究，结合低温扫描电子显微镜（LTSEM）的空间分辨分析，以及基于准经典Eilenberger方程的理论建模，将提供对具有定制界面和势垒的d波超导体斜坡型结的输运过程的理解。（ii）二维（2D）超导量子干涉滤波器（sqif）的实现和研究。sqif是约瑟夫森结干涉仪，按照特定的统计分布设计成超导环路的不规则排列。这种结网络可以定制，以显示对磁场的特征响应，从而可以测量具有极高灵敏度，线性度和动态范围的绝对磁场。2D YBCO sqif特别适用于60k以上的单级制冷机。除了检测静态和低频磁场外，这种sqif还可以设计成极宽带的电磁信号传感器、前置放大器和混频器（Ka波段的长波到卫星频率）。这为超导电子学在通信技术中的应用开辟了新的前景。

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.