π phase shifter based on NbN-based ferromagnetic Josephson junction on a silicon substrate

Taro Yamashita, Sunmi Kim, Haruki Kato, Wei Qiu, Kouichi Semba, Akira Fujimaki, Hirotaka Terai
2020 Scientific Reports  
In the field of superconducting electronics, a π phase shifter based on a ferromagnetic Josephson junction is expected to provide various advantages to classical and quantum superconducting devices. Here we report niobium nitride (NbN)-based ferromagnetic π junctions on a silicon (Si) substrate with a titanium nitride (TiN) buffer layer, which have applications to flux-bias-free flux quantum bits (qubits) and classical digital logic elements. We fabricated and characterized NbN/aluminum nitride
more » ... bN/aluminum nitride (AlN)/NbN Josephson junctions, NbN/copper nickel (CuNi)/NbN ferromagnetic Josephson junctions, and superconducting quantum interference devices (SQUIDs) consisting of these junctions on the Si substrate. The fabricated NbN/AlN/NbN junctions showed a high junction quality suitable for qubit applications. Furthermore, the magnetic field dependence of the SQUID's critical current indicated that the NbN/CuNi/NbN junction worked as a π phase shifter on the Si substrate.
doi:10.1038/s41598-020-70766-9 pmid:32792626 fatcat:4sx3ysrnc5bvhb5yvbya6zkwye