Fabrication and characterization of micropillar Josephson junction with Niobium Nitride and Permalloy/Samarium Cobalt exchange spring magnet
POSTER
Abstract
Adam Bowen, Jiyeong Gu
Department of Physics and Astronomy, California State University, Long Beach, Long Beach, CA 90840
Superconductors are prevalent in cutting-edge technology and research, such as MRI, quantum computers, and particle accelerators. The superconducting proximity effect occurs when the superconductor is adjacent to non-superconducting material since the superconducting condensate, pairs of electrons known as Cooper pairs, leaks into a non-superconducting material. We fabricated micropillar Josephson junctions in hybrid superconductors and attempted to observe the odd triplet effect of superconductor (S)/ferromagnet (F)/superconductor (S/F/S) system. First Nb was used for S and a ferromagnetic exchange spring system of Permalloy (Py) and Samarium Cobalt (SmCo) were used for F. Due to the low superconducting critical temperature (Tc) of Nb we had a difficulty measuring the Josephson current in S/F/S junction. Therefore, in this work we introduce new superconductor NbN which has much higher bulk Tc. We found Tc increased a lot from ~3.3 K for 100 nm Nb thin film to ~9.3 K for 100 nm NbN thin film. To optimize Tc of NbN thin film, N2 gas was introduced during the magnetron sputtering process. NbN thin films at different ratio of N2/Ar gas were made and Tc dependence on the ratio was investigated.
Department of Physics and Astronomy, California State University, Long Beach, Long Beach, CA 90840
Superconductors are prevalent in cutting-edge technology and research, such as MRI, quantum computers, and particle accelerators. The superconducting proximity effect occurs when the superconductor is adjacent to non-superconducting material since the superconducting condensate, pairs of electrons known as Cooper pairs, leaks into a non-superconducting material. We fabricated micropillar Josephson junctions in hybrid superconductors and attempted to observe the odd triplet effect of superconductor (S)/ferromagnet (F)/superconductor (S/F/S) system. First Nb was used for S and a ferromagnetic exchange spring system of Permalloy (Py) and Samarium Cobalt (SmCo) were used for F. Due to the low superconducting critical temperature (Tc) of Nb we had a difficulty measuring the Josephson current in S/F/S junction. Therefore, in this work we introduce new superconductor NbN which has much higher bulk Tc. We found Tc increased a lot from ~3.3 K for 100 nm Nb thin film to ~9.3 K for 100 nm NbN thin film. To optimize Tc of NbN thin film, N2 gas was introduced during the magnetron sputtering process. NbN thin films at different ratio of N2/Ar gas were made and Tc dependence on the ratio was investigated.
*This project is mainly supported in part by the 2024 ORED Summer Student Research Assistantship and 2023 Google Summer Research Assistantship. This work was also partially supported by the Partnership for Research and Education in Materials (PREM) program between California State University, Long Beach and The Ohio State through a grant from the National Science Foundation under Grant No. 2122199.
Presenters
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Adam R Bowen
- California State University, Long Beach