High-Tc Josephson devices for near-field biomagnetism

Research Project, 2023 – 2026

The objective of this proposal is to provide the necessary technology for a scalable high-transition temperature (high-Tc) superconducting (HTS) Josephson junction (JJ) device technology and to develop the next generation high-Tc superconducting quantum interference device (SQUID) based multichannel near-field biomagnetic systems for, e.g., near-field magnetoencephalography (MEG) neuroscience research. To this date, several studies with our present 7-channel HTS near-field MEG system have shown superior spatial resolution and information content even with this low number of channels. Signals not seen by conventional state-of-art commercial MEG-system were observed and most strikingly, a clinical benchmark case study on interictal epileptiform discharges (IEDs) revealed twice as many IEDs with our HTS MEG system compared to conventional MEG and 3 times compared to EEG for this individual. In order to have clinically viable systems, larger sensor arrays made from reproducible JJs are needed. However, due to the short coherence length in HTS, this is a challenge in all HTS interface JJ technologies, and results in poor reproducibility and scalability. By instead changing the local order, e.g., from geometry and/or local doping profiles, of a short thin "Dayem"-bridge, we propose to give the superconducting phase change a more "adiabatic" and controllable form across the junctions mitigating the problems of tunnel barriers and sharp interfaces in the transport direction.