Superconducting Devices for Cryogenic and Quantum Computing
π Junctions
Critical Josephson current oscillations – an experimental signature of the π junction. From Satchell et al. Sci. Rep. 11, 11173 (2021)
π junctions are a special case of Josephson junctions where the ground-state phase difference across junction is π as opposed to the usual zero. π junctions have been proposed as circuit elements in superconducting digital logic and in certain qubit designs for quantum computing. It is possible to achieve a π junction by using a ferromagnet as the barrier in the junction and tuning precisely the thickness of the ferromagnet. In the past, Satchell has studied magnetic materials with perpendicular magnetic anisotropy for this application.
For an in depth review of Josephson π junctions, see the recent article Birge and Satchell APL Mater. 12 (4): 041105 (2024).
Supercurrent Diodes
Supercurrent diode effect in a niobium track under applied field. From Satchell et al. JAP 133, 203901 (2023).
The supercurrent diode is an analog to rectification in semiconductor pn junctions, where current is allowed to flow only in one direction. In the supercurrent diode, the critical current of the device is nonreciprocal, leading to the situation where a dissipationless supercurrent can pass in one direction, but upon reversing the current direction, the device becomes resistive. It has been suggested that a supercurrent diode may become a useful component for digital processing in a superconducting computer.
Unconventional Superconductors
Unconventional superconductors are a topic of intense research effort for both their novel physics and potential for application in future computing. Unconventional superconductivity is an incredibly broad research area, particularly since the catch-all term applies to many systems, including high-Tc’s, iron pnictides, and chalcogenides, organics, heavy fermion, and topological materials, each with its unique properties and potential applications.
The SUPERMAG Lab focuses on unconventional superconducting materials with a spin-triplet component, where the two electrons in the Cooper pair align parallel instead of antiparallel. The importance of studying unconventional superconducting materials with spin-triplets is that understanding this unconventional mechanism pushes the boundaries of our knowledge of condensed matter physics, and spin-triplets provide a platform for testing theoretical models and exploring emergent phenomena in quantum materials. In addition to these exotic properties, an unconventional superconductor with spin-triplet physics opens possible applications, including combining superconductivity with magnetism in superspintronic logic and memory devices for digital computing, as well as novel qubits for quantum computing.
Publications
See ORCID or Google Scholar for a complete list of publications.