Demonstration of Integrated SIS/SFS Memory Unit Cell

Through the assembly of a hybrid ferromagnetic (F)/superconducting (S) system, it is possible to create novel technologies that can be utilized in the cryogenic computing world. When assembling Josephson junctions that use a magnetic pseudo-spin valve as the coupling layer, one can exploit the phase characteristics of the junction to act as a persistent non-volatile memory bit. This arises as a result of the relative orientation of the magnetizations of the two F layers, either parallel or antiparallel, yielding an equilibrium phase of 0 or π across the junction [1]. This binary behavior can be read out by a SQUID based on traditional insulating (I) Josephson junctions, and is ideal for classical computing technologies based on superconducting materials [2]. In order to realize such an application, SIS Josephson junctions must be integrated in a single fabrication process with SFS pseudo-spin valve junctions. We present here an unambiguous demonstration of a working integrated SIS/SFS memory device based on these concepts.

[1] Gingrich, E. C., et al. Nature Physics 12.6 (2016): 564-567.

[2] Holmes, D. Scott, et al. IEEE Transactions on Applied Superconductivity 23.3 (2013): 1701610-1701610.