Monday , January 18 2021

Supercomputers without waste heat

Scanning tunneling microscope installed in a helium cooling device seen from below (with sample phase removed). The mechanism for positioning the microscope tip over the sample surface is visible (center of the image). Credit: Simon Diesch

Generally, magnetism and the loss of electrical current ("superconductivity") are competing phenomena that can not exist in the same sample. But to build supercomputers, the synergistic combination of both states has great advantages over today's semiconductor technology, which is characterized by high power consumption and heat production. Researchers at the Institute of Physics at Konstanz University have now demonstrated that the loss-free electrical transmission of magnetically encoded information is possible. This finding enables improved storage density on integrated circuit boards and significantly reduces energy consumption in data processing centers. The results of this study have been published in the current edition of the scientific journal nature Communications.

The miniaturization of semiconductor technology approaches its physical limits. For more than 70 years, information processing in computers has been realized by creating and transmitting electrical signals that release heat waste. Heat dissipation results in a rise in temperature in the building blocks, which in turn requires complex refrigeration systems. Heat treatment is one of the major challenges in miniaturization. Therefore, efforts are currently being made to reduce waste heat in data processing and telecommunications worldwide.

A collaboration at the University of Konstanz between the experimental physics group led by Professor Elke Scheer and the theoretical physics group led by Professor Wolfgang Belzig uses an approach based on dispersal transport in superconducting building blocks. Magnetic materials are often used for storing information. Magnetically encoded information can, in principle, also be transported without heat production using electron spin instead of charging. Combination of loosely conveying superconductivity with the electronic transport of magnetic information, ie. Spintronics paves the way for fundamentally new functionalities for future energy-efficient information technologies.

The University of Konstanz researchers have taken a major challenge in this approach: the fact that in conventional superconductors the flow of pairs of electrons with opposite magnetic moments is carried. These pairs are therefore non-magnetic and can not carry magnetic information. The magnetic state, on the other hand, is formed by magnetic moments which are parallel to each other and thereby suppress superconducting current.

"The combination of superconductivity, which works without heat generation, with spintronics, transmits magnetic information, does not oppose any basic physical concepts, but only naive assumptions about the nature of the materials," says Elke Scheer. Recent results indicate that by bringing superconductors into contact with special magnetic materials, electrons with parallel spins can bind to pairs that carry super power over longer distances through magnets. This concept can enable new electronic devices with revolutionary features.

Under the supervision of Elke Scheer, Dr. Simon Diesch an experiment that clarifies the creation mechanism for such electron pairs with parallel spin orientation. "We showed that it is possible to create and discover these centrifuged electron pairs," explains Simon Diesch. The system's design and interpretation of the measurement results are based on the doctoral dissertation's doctoral dissertation, conducted under the supervision of Wolfgang Belzig.

"It is important to find materials that allow such aligned electron pairs. We are therefore not just a physics but also a material science project," says Scheer. Researchers from the Karlsruhe Institute of Technology (KIT) provided tailor-made samples consisting of aluminum and europium sulfide. Aluminum is a very well-researched superconductor that allows for a quantitative comparison between theory and experiment. Europium sulfide is a ferromagnetic insulator, an important material feature for the realization of the theoretical concept, which maintains its magnetic properties even in very thin layers with only a few nanometers in thickness as used herein. Using a scan tunnel microscope developed at the University of Konstanz, spatial and energetically read measurements of the charge transport of aluminum-europium sulfide samples were performed at low temperatures. Unlike commercial instruments, the scan tunnel microscope is based on the Scheer Label optimized for ultimate energy solution and for operation in different magnetic fields.

The voltage dependence of the charge transport through the samples is indicative of the energy process of the electron pairs and allows accurate determination of the superconductive state composition. To this end, a theory previously developed by the Belzig group and tailored to describe the aluminum-europium sulfide interface was used. This theory will enable researchers to describe much more complex electrical circuits and tests in the future. The energy spectra predicted by the theory are consistent with the experimental findings that provide direct evidence of magnetic electron pairs.

In addition, experimental-theoretical collaboration solved existing contradictions regarding the interpretation of such spectra. With these results, the University of Konstanz physicists hope to reveal the high potential of superconductive spintronics to improve or replace semiconductor technology.

Explore further:
Some superconductors can also carry streams of & # 39; spin & # 39;

More information:
S. Diesch et al. Creating equal-spin triplet superconductivity at the Al / EuS interface, nature Communications (2018). DOI: 10,1038 / s41467-018-07597-w

Journal reference:
nature Communications

Supplied by:
University of Konstanz

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