March 22, 2016

Russians have concept for superconductor memory hundreds of times faster than conventional computer memory with picosecond access

Russian scientists claim to have invented a new superconducting memory architecture that will be 100s of times faster and consume dozens of times less power than conventional memory chips. The Moscow Institute of Physics and Technology (MIPT, Russia) working with the Moscow State University (MSU, Russia) claim the architecture can also be used to perform single-flux quantum logic operations for superconducting processors, but admits that commercialization is decades away.

"What we have so far is an idea, a concept," Alexander Golubov, the head of Moscow Institute of Physics and Technology’s Laboratory of Quantum Topological Phenomena in Superconducting Systems told EE Times. "We expect its proof of principle experiment to be commenced in the near future." After proof of principle, the researchers will begin a "construction testing stage, where the selection of materials and optimization of the topology will be made," said Golubov. "It's hard to evaluate even the approximate time of the technology's possible commercialization, but it's probably decades away."

Diagram of the junction. S – superconductor, I – insulating tunnel barrier, F – ferromagnet, N – normal metal, shaded area – potential barrier arising in the superconducting zone. (Source: Moscow Institute of Physics and Technology)

The unique part of the MIPT/MSU project is a new type of superconducting junction and memory architecture. Normal Josephson junctions use sandwiches of superconductor-insulator-superconductor such as in D-Wave's quantum computer, but MIPT/MSU's memory uses adds a normal-metal/ferromagnetic-metal (N/F) interlayer adjacent the insulator to achieve two stable conduction currents that can quickly switch between 1s and 0s. Since superconductors conduct current with zero resistance, the two stable states should take no energy to maintain, argue the scientists in their paper.

The MIPT/MSU researchers claim that read and write operations will be hundreds or even thousands of times faster than with conventional ferromagnetic memory technologies--depending on the final materials formulation--taking just a few hundred picoseconds to switch a 0 to a 1 or visa versa.

Applied Physics Letters - Superconducting phase domains for memory applications

In this work, we study theoretically the properties of S-F/N-sIS type Josephson junctions in the frame of the quasiclassical Usadel formalism. The structure consists of two superconducting electrodes (S), a tunnel barrier (I), a combined normal metal/ferromagnet (N/F) interlayer, and a thin superconducting film (s). We demonstrate the breakdown of a spatial uniformity of the superconducting order in the s-film and its decomposition into domains with a phase shift π. The effect is sensitive to the thickness of the s layer and the widths of the F and N films in the direction along the sIS interface. We predict the existence of a regime where the structure has two energy minima and can be switched between them by an electric current injected laterally into the structure. The state of the system can be non-destructively read by an electric current flowing across the junction.

SOURCES - applied physics Letters, EEtimes

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