From The California Institute of Technology: “New theory explains magnetic trends in high-temperature superconductors” 

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From The California Institute of Technology

11.30.22
Emily Velasco
(626) 372‑0067
evelasco@caltech.edu

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In just about any situation in which electricity is being used, whether it is lighting a bedroom at night, keeping frozen food cold, or powering a car that is taking a commuter to work, some of that electrical energy is lost as heat. This is called resistance. Materials with lower resistance are better at conducting electricity while materials with higher resistance are worse at it.

Though nearly all conductors exhibit some resistance, there are some materials that have no electrical resistance whatsoever. These are called superconductors, and their unique properties are used in technologies ranging from magnetic resonance imaging (MRI) to levitating trains.

However, most superconductors only superconduct when they are cold—really cold. Even so-called “high temperature” superconductors need to be cooled with liquid nitrogen to roughly -200 degrees Celsius to work.

That need for intense cooling adds a big complication to the use of superconductors. For decades, researchers have sought out superconductors that work at room temperature. Currently, at normal atmospheric pressure, the class of high temperature superconductors known as the cuprates—compounds containing both copper and oxygen atoms—come the closest, with the best-performing cuprate able to superconduct at temperatures as “warm” as -140 degrees Celsius.

Since -140 degrees Celsius is still quite cold, there is a long way to go before cuprates can be called room-temperature superconductors, and further advancement of these superconductors has been hampered by the fact that no one has figured out how cuprate superconductors work.

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Garnet Chan, Bren Professor of Chemistry at Caltech. Credit: Caltech.

But now, researchers in the group of Garnet Chan, Caltech’s Bren Professor of Chemistry, have developed a theory that explains some of the magnetic properties of cuprate superconductors. Cuprate superconducting materials exhibit a layer effect, where their magnetic and superconducting properties are enhanced as more layers of the constituent copper and oxygen atoms are brought together. In a paper published in the journal Science [below], Chan and his coauthors explain how the magnetic layer effect arises from fluctuations of the electrons between the copper and oxygen atoms and their surrounding atoms.

“This is a first step toward understanding the governing principles behind the superconducting layer effect, and what controls the superconducting temperature in superconductors more generally,” says Zhihao Cui, chemistry graduate student and first author of the study.

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Zhihao Cui. Credit: Caltech.

Science paper:
Science

See the full article here .

Comments are invited and will be appreciated, especially if the reader finds any errors which I can correct.


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The California Institute of Technology is a private research university in Pasadena, California. The university is known for its strength in science and engineering, and is one among a small group of institutes of technology in the United States which is primarily devoted to the instruction of pure and applied sciences.

The California Institute of Technology was founded as a preparatory and vocational school by Amos G. Throop in 1891 and began attracting influential scientists such as George Ellery Hale, Arthur Amos Noyes, and Robert Andrews Millikan in the early 20th century. The vocational and preparatory schools were disbanded and spun off in 1910 and the college assumed its present name in 1920. In 1934, The California Institute of Technology was elected to the Association of American Universities, and the antecedents of National Aeronautics and Space Administration ‘s Jet Propulsion Laboratory, which The California Institute of Technology continues to manage and operate, were established between 1936 and 1943 under Theodore von Kármán.

The California Institute of Technology has six academic divisions with strong emphasis on science and engineering. Its 124-acre (50 ha) primary campus is located approximately 11 mi (18 km) northeast of downtown Los Angeles. First-year students are required to live on campus, and 95% of undergraduates remain in the on-campus House System at The California Institute of Technology. Although The California Institute of Technology has a strong tradition of practical jokes and pranks, student life is governed by an honor code which allows faculty to assign take-home examinations. The The California Institute of Technology Beavers compete in 13 intercollegiate sports in the NCAA Division III’s Southern California Intercollegiate Athletic Conference (SCIAC).

As of October 2020, there are 76 Nobel laureates who have been affiliated with The California Institute of Technology, including 40 alumni and faculty members (41 prizes, with chemist Linus Pauling being the only individual in history to win two unshared prizes). In addition, 4 Fields Medalists and 6 Turing Award winners have been affiliated with The California Institute of Technology. There are 8 Crafoord Laureates and 56 non-emeritus faculty members (as well as many emeritus faculty members) who have been elected to one of the United States National Academies. Four Chief Scientists of the U.S. Air Force and 71 have won the United States National Medal of Science or Technology. Numerous faculty members are associated with the Howard Hughes Medical Institute as well as National Aeronautics and Space Administration. According to a 2015 Pomona College study, The California Institute of Technology ranked number one in the U.S. for the percentage of its graduates who go on to earn a PhD.

Research

The California Institute of Technology is classified among “R1: Doctoral Universities – Very High Research Activity”. Caltech was elected to The Association of American Universities in 1934 and remains a research university with “very high” research activity, primarily in STEM fields. The largest federal agencies contributing to research are National Aeronautics and Space Administration; National Science Foundation; Department of Health and Human Services; Department of Defense, and Department of Energy.

In 2005, The California Institute of Technology had 739,000 square feet (68,700 m^2) dedicated to research: 330,000 square feet (30,700 m^2) to physical sciences, 163,000 square feet (15,100 m^2) to engineering, and 160,000 square feet (14,900 m^2) to biological sciences.

In addition to managing NASA-JPL/Caltech , The California Institute of Technology also operates the Caltech Palomar Observatory; the Owens Valley Radio Observatory;the Caltech Submillimeter Observatory; the W. M. Keck Observatory at the Mauna Kea Observatory; the Laser Interferometer Gravitational-Wave Observatory at Livingston, Louisiana and Hanford, Washington; and Kerckhoff Marine Laboratory in Corona del Mar, California. The Institute launched the Kavli Nanoscience Institute at The California Institute of Technology in 2006; the Keck Institute for Space Studies in 2008; and is also the current home for the Einstein Papers Project. The Spitzer Science Center, part of the Infrared Processing and Analysis Center located on The California Institute of Technology campus, is the data analysis and community support center for NASA’s Spitzer Infrared Space Telescope [no longer in service].

The California Institute of Technology partnered with University of California at Los Angeles to establish a Joint Center for Translational Medicine (UCLA-Caltech JCTM), which conducts experimental research into clinical applications, including the diagnosis and treatment of diseases such as cancer.

The California Institute of Technology operates several Total Carbon Column Observing Network stations as part of an international collaborative effort of measuring greenhouse gases globally. One station is on campus.