Switchable Superconducting Josephson Junction Device for Low Energy Information Storage and Processing
Exchange field junctions enables supercurrent found in field sensors (both magnetic and electric), measurement standards, or in quantum computing.
Researchers
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switchable superconducting josephson junction device for low energy information storage and processing
United States of America | Granted | 10,741,744
Figures
A switchable Josephson junction 34 having two superconducting layers (SC1 and SC2) where SC1 is sandwiched between two ferromagnetic insulator layers (F1 and F2). At a temperature below the critical superconducting temperature of the SC layers, the conducting state of SC1 can be switched between a normal metal (NM) and a superconductor by the relative magnetic alignment of the neighboring FI layers. When the magnetization of the layers F1 and F2
The layer sequence of the device with the numbers in parentheses corresponding to thickness in nm. In these structures, the SC electrodes 6, 10 are separated by GdN tunnel barriers. The combination of a thin AlN layer 14 followed by a thick Al layer 16 was found to be the best capping to protect samples from degradation while preserving vertical transport.
Technology
The exchange field based junction consists of an alternating superconductor (SC) and ferromagnetic insulator (FI) multilayer in the order SC/FI/SC/FI. Due to IEF, the upper part of the device can operate as a Josephson junction when the two ferromagnets are magnetized antiparallel. However, in the case of parallel magnetization, the structure suppresses superconductivity resulting in significantly decreased current for a millivolt bias. This binary system is both nonvolatile and observable as an enormous change in device resistance. The conductive state is controlled by the relative magnetization orientation of the neighboring ferromagnetic insulators. Magnetization orientation can be set with a topological insulator and a high atomic number layer. A gate voltage is applied between the topological insulator and the high atomic number layer, causing a change in the ferromagnetic layer through spin-orbit-coupling.
Problem Addressed
Spin-electronic (spintronics) memory uses electron spin for logic and sensing. Heat loss from associated charge currents limits the potential applications in computing technology. Superconducting electronics do not rely on spin and offer a loss-less alternative with significantly higher clock speeds. The Josephson junction is a versatile superconducting device that uses Interfacial Exchange Field (IEF) from ferromagnetic insulators to control conventional superconductivity. For standard von Neumann architectures, memory and logic are separated, thus adding to computation time. The presented technology integrates a nonvolatile memory and readout in the same structure at ultralow power and ultrafast computation time.
Advantages
- Integration of memory and readout decrease computation time and increase processing speeds
- Josephson junctions have no power dissipation so energy and operation costs are saved
- Made by sputtering technique so design is easily scalable into an ultra-dense array
Publications
Juan Pedro Cascales,et al. "Switchable Josephson Junction Based on Interfacial Exchange Field." Applied Physics Letters, January 14, 2019, 114 (2): 022601. https://doi.org/10.1063/1.5050382.
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