超伝導体とは何か？

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Become a Member in Seconds Unlock instant access to exclusive member features. Contact me with news and offers from other Future brands Receive email from us on behalf of our trusted partners or sponsors By submitting your information you agree to the Terms & Conditions and Privacy Policy and are aged 16 or over. You are now subscribed Your newsletter sign-up was successful Want to add more newsletters? Delivered Daily Daily Newsletter Sign up for the latest discoveries, groundbreaking research and fascinating breakthroughs that impact you and the wider world direct to your inbox. Signup + Once a week Life's Little Mysteries Feed your curiosity with an exclusive mystery every week, solved with science and delivered direct to your inbox before it's seen anywhere else. 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What are superconductors used for? Latest research The future of superconductors Additional resources Superconductors are used in a variety of applications, such as the Shanghai Maglev Train, also known as the Shanghai Transrapid, a high-speed magnetic levitation train. (Image credit: Getty Images/ Christian Petersen-Clausen) Jump to category: Who discovered superconductivity? History of superconductivity How do superconductors work? What are superconductors used for? Latest research The future of superconductors Additional resources Share Copy link Facebook X Reddit Pinterest Flipboard Share this article Join the conversation Follow us Add us as a preferred source on Google Newsletter Subscribe to our newsletter A superconductor is a material that achieves superconductivity, which is a state of matter that has no electrical resistance and does not allow magnetic fields to penetrate. An electric current in a superconductor can persist indefinitely. Superconductivity can only typically be achieved at very cold temperatures. Superconductors have a wide variety of everyday applications, from MRI machines to super-fast maglev trains that use magnets to levitate the trains off the track to reduce friction. Researchers are now trying to find and develop superconductors that work at higher temperatures, which would revolutionize energy transport and storage. Who discovered superconductivity? The credit for the discovery of superconductivity goes to Dutch physicist Heike Kamerlingh Onnes . In 1911, Onnes was studying the electrical properties of mercury in his laboratory at Leiden University in The Netherlands when he found that the electrical resistance in the mercury completely vanished when he dropped the temperature to below 4.2 Kelvin — that's just 4.2 degrees Celsius (7.56 degrees Fahrenheit) above absolute zero. You may like Physicists push quantum boundaries by turning a superfluid into a supersolid — and back — for the first time 'Thermodynamic computer' can mimic AI neural networks — using orders of magnitude less energy to generate images Why is mercury a liquid? To confirm this result, Onnes applied an electric current to a sample of supercooled mercury, then disconnected the battery. He found that the electric current persisted in the mercury without decreasing, confirming the lack of electrical resistance and opening the door to future applications of superconductivity. History of superconductivity Physicists spent decades trying to understand the nature of superconductivity and what caused it. They found that many elements and materials, but not all, become superconducting when cooled below a certain critical temperature. In 1933, physicists Walther Meissner and Robert Ochsenfeld discovered that superconductors "expel" any nearby magnetic fields, meaning weak magnetic fields can't penetrate far inside a superconductor, according to Hyper Physics , an educational site from the Georgia State University department of physics and astronomy. This phenomenon is called the Meissner effect. It wasn't until 1950 that theoretical physicists Lev Landau and Vitaly Ginzburg published a theory of how superconductors work, according to Ginzburg's biography on The Nobel Prize website . While successful in predicting the properties of superconductors, their theory was "macroscopic," meaning it focused on the large-scale behaviors of superconductors while remaining ignorant of what was going on at a microscopic level. Sign up for the Live Science daily newsletter now Get the world’s most fascinating discoveries delivered straight to your inbox. Contact me with news and offers from other Future brands Receive email from us on behalf of our trusted partners or sponsors Finally, in 1957, physicists John Bardeen, Leon N. Cooper and Robert Schrieffer developed a complete, microscopic theory of superconductivity. To create electrical resistance, the electrons in a metal need to be free to bounce around. But when the electrons inside a metal become incredibly cold, they can pair up, preventing them from bouncing around. These electron pairs, called Cooper pairs, are very stable at low temperatures, and with no electrons "free" to bounce around, the electrical resistance disappears. Bardeen, Cooper and Schrieffer put these pieces together to form their theory, known as BCS theory, which they published in the journal Physical Review Letters . How do superconductors work? When a metal drops below a critical temperature, the electrons in the metal form bonds called Cooper pairs. Locked up like this, the electrons can't provide any electrical resistance, and electricity can flow through the metal perfectly, according to the University of Cambridge . However, this only works at low temperatures. When the metal gets too warm, the electrons have enough energy to break the bonds of the Cooper pairs and go back to offering resistance. That is why Onnes, in his original experiments, found that mercury behaved as a superconductor at 4.19 K, but not 4.2 K. What to read next Earth is 'missing' lighter elements. They may be hiding in its solid inner core. IBM quantum processor achieves highest fidelity calculations for the longest period of time on record Physicists witness pinpricks of darkness moving faster than the speed of light What are superconductors used for? It's very likely that you've encountered a superconductor without realizing it. In order to generate the strong magnetic fields used in magnetic resonance imaging (MRI) and nuclear magnetic resonance imaging (NMRI), the machines use powerful electromagnets, as described by the Mayo Clinic . These powerful electromagnets would melt normal metals due to the heat of even a little bit of resistance. However, because superconductors have no electrical resistance, no heat is generated, and the electromagnets can generate the necessary magnetic fields. Similar superconducting electromagnets are also used in maglev trains, experimental nuclear fusion reactors and high-energy particle accelerator laboratories.Superconductors are also used to power railguns and coilguns, cell phone base stations, fast digital circuits and