![]() ![]() By contrast, regular superconducting quantum interference devices 21, 22 are characterized by a periodic dependence on the external field and thus do not allow absolute field measurements. The zeroth-order critical current interference peak is significantly sharper and taller than all other maxima, thus allowing absolute magnetic field measurements. The interference peak is so narrow that it allowed us to distinguish magnetic fields which differ by about 8 nT, using a simple dc technique. We observe an extreme sensitivity of the array to perpendicular external magnetic fields, which is explained in terms of the diffraction-grating-style interference of supercurrents in many parallel junctions. Constructive interference of the supercurrents in multiple parallel superconducting nanowires has been discussed theoretically previously 20. We find that such a proximitized array acts as a superconducting analog of the optical diffraction grating. ![]() In our work, we demonstrate that it is possible to establish high critical current and good contact, hence stronger proximity. Yet, previous reports 2 suggested that it is very difficult, if not impossible, to introduce a significant proximity superconductivity into the intrinsic topological insulator, BST 2. There are theoretical predictions suggesting that BST can be used to build superconducting qubits for topologically protected quantum computers 19. The focus of our study is a square array of superconducting Niobium islands overlaying an intrinsic topological insulator film Bi 0.8Sb 1.2Te 3 (BST) 2. Correspondingly, in the fully superconducting regime, the kinetic inductance would be dependent on the supercurrent polarity. Such a device should have zero resistance at one current polarity and a nonzero resistance at the opposite polarity. Therefore, a superconducting rectifier or a diode, characterized by zero resistance, remains highly desired for computational, sensing, and communication applications with ultralow power consumption. But, due to their finite resistance, Joule heating and energy losses are inevitable in such devices. The diode effect is used in a number of very important electronic components, including photodetectors, ac rectifiers, and frequency multipliers. They exhibit either a high or low resistance, depending on the current polarity. ![]() Generally speaking, nonreciprocal phenomena are well-known in relation to semiconductor diodes, which are based on p-n junctions. Recently, a theoretical model was proposed, predicting that Majorana bound states, if present, can generate a parity-protected diode effect, due to their exotic current-phase relationship 18. It was also reported that Mo-Ge perforated films could be patterned using a conformal mapping approach in order to create superconducting diodes 17. Previously, superconducting rectifiers have been realized in asymmetric superconducting nanowire loops 15, 16. ![]() A magnetically controllable superconducting diode has been demonstrated in, n, an artificial superlattice without a center of inversion 14. These are sought after due to the promise of topologically protected quantum computation.Īnother phenomenon that has attracted attention recently is the superconducting diode effect 8, 9, 10, 11, 12, 13. Moreover, arrays can provide room for multiple interacting vortices, which may be subjected to quantum braiding manipulations. Various SQUIF systems 5, 6 are interesting for applications since they contain many interfering superconducting loops and thus enable absolute magnetic field sensitivity 7. Although single junctions and SQUIDs have been previously studied in great depth, topological superconductor arrays, and superconducting quantum interference filters (SQIFs) have not been sufficiently investigated. They continue to be a hot topic in condensed matter physics due to the predicted and, to some extent, observed signatures of Majorana zero modes 4. Such hybrid structures provide a testing ground for topological superconductivity 3. Topological insulator (TI) films can be made superconducting, using the proximity effect, by placing superconducting electrodes on the TI surface 1, 2. ![]()
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