Superconductors are materials that realize superconductivity, State of matter It has no electrical resistance and does not transmit magnetic fields.Ann Current Superconductors can survive indefinitely.
Superconductivity can usually only be achieved at very low temperatures. For superconductors MRI device For ultra-high-speed linear motor cars that use magnets to lift trains off track and reduce friction. Researchers are now trying to find and develop superconductors that function at high temperatures that will revolutionize the transport and storage of energy.
Who discovered superconductivity?
The achievement of the discovery of superconductivity Dutch physicist Heike Kamerlingh Onnes.. In 1911, Onness was studying the electrical properties of Mercury When he discovered in his laboratory at Leiden University in the Netherlands that the electrical resistance of mercury had completely disappeared when he dropped it. temperature Less than 4.2 Kelvin — just 4.2 ° C (7.56 ° F) above absolute zero.
To confirm this result, Onness energized a sample of supercooled mercury and disconnected the battery. He discovered that the current persisted in mercury without diminishing, confirmed the lack of electrical resistance, and opened the door to future applications of superconductivity.
History of superconductivity
Physicists have spent decades trying to understand the nature of superconductivity and its causes. They have found that many, but not all, elements and materials become superconducting when cooled below a certain critical temperature.
In 1933, physicists Walther Meissner and Robert Ochsenfeld discovered that superconductors “emit” a nearby magnetic field. In other words, a weak magnetic field cannot penetrate deep into the superconductor. Hyperphysics, Georgia State University Physics and Astronomy Department Education Site. This phenomenon is called the Meissner effect.
It wasn’t until 1950 that theoretical physicists Lev Landau and Vitaly Ginsburg published their theory of how superconductors work. Nobel Prize website.. While they succeeded in predicting the properties of superconductors, their theory was “microscopic.” That is, we focused on the large-scale behavior of superconductors without knowing what was happening at the microscopic level.
Finally, in 1957, physicists John Bardeen, Leon N. Cooper, and Robert Schrieffer developed a complete microscopic theory of superconductivity. To create an electrical resistance Electronic You need to bounce freely in the metal. But when the electrons inside the metal get incredibly cold, they pair and prevent them from bouncing back. These electron pairs, called Cooper pairs, are very stable at low temperatures and have no electrical resistance because there are no “free” bouncing electrons. Bardeen, Cooper, and Schrieffer combined these elements to form a theory known as BCS theory, which was published in the journal. Physical review letter..
How do superconductors work?
When the metal falls below the critical temperature, the electrons in the metal form a bond called a Cooper pair. When confined in this way, the electrons cannot provide electrical resistance and electricity can flow completely through the metal. University of Cambridge..
However, this only works at low temperatures. If the metal gets too warm, the electrons have enough energy to break the Cooper pair bond and return to provide resistance. So, in his first experiment, Onness discovered that mercury behaves as a superconductor at 4.19 K, but not at 4.2 K.
What are superconductors used for?
It is highly possible that you encountered a superconductor without noticing it. To generate the strong magnetic fields used in magnetic resonance imaging (MRI) and magnetic resonance imaging (NMRI), the machine Mayo Clinic.. These powerful electromagnets melt ordinary metals due to the heat of the slightest resistance. However, because superconductors have no electrical resistance, they do not generate heat and electromagnets can generate the required magnetic fields.
Similar superconducting electromagnets are also used in linear motor cars, experimental fusion reactors, and high-energy particle accelerator laboratories. Superconductors are also used in railguns and coilguns, mobile phone base stations, high-speed digital circuits, and particle detectors.
Basically, if you need a very strong magnetic field or current and you don’t want the device to melt the moment you turn it on, you need a superconductor.
Alexey Bezryadin, a condensed matter physicist at the University of Illinois at Urbana-Champaign, said: Due to the unique properties of superconductor currents, they can be used to build quantum computers.
“Such computers are made up of qubits or qubits. Unlike classical information bits, qubits can exist in a” 0 “and” 1 “quantum superposition state at the same time. Superconducting devices can mimic this, “Bezriadin told Live Science. .. “For example, the current in a superconducting loop can flow clockwise and counterclockwise at the same time. Such a state constitutes an example of a superconducting qubit.”
What is the latest information on superconductor research?
“Currently, superconductivity exists only at very low temperatures or very high pressures, so the first challenge for researchers today is superconductors in ambient conditions,” said Mehmet Dogan, a postdoctoral fellow at the University of California, Berkeley. Is to develop a material that is. ” The next challenge is to explain how new superconductors work and develop theories to predict the properties of those materials, Dogan told Live Science in an email.
Superconductors fall into two main categories: cryogenic superconductors (LTS), also known as conventional superconductors, and high-temperature superconductors (HTS) or non-conventional superconductors. LTS can be explained by BCS theory, which explains how electrons form Cooper pairs, but HTS uses other microscopic methods to achieve zero resistance. The origin of HTS is one of the major open problems in modern physics.
Most of the historical research on superconductivity has been directed towards LTS. Because those superconductors are much easier to discover and study, almost every application of superconductivity involves LTS.
In contrast, HTS is an active and exciting area of modern research. Anything that acts as a superconductor above 70 K is generally considered HTS. It’s still pretty cold, but that temperature is desirable as it can be reached by cooling with liquid nitrogen. Liquid nitrogen is much more common and readily available than liquid helium, which is required to cool to the lower temperatures required for LTS.
The future of superconductors
The “Holy Grail” of superconductor research is to find materials that can function as superconductors at room temperature. to date, Maximum superconducting temperature It was reached with an extremely pressurized carbonaceous sulfur hydride and reached superconductivity at 59 F (15 C, or about 288 K), which required a pressure of 267 gigapascals. Its pressure is comparable to the interior of a giant planet like Jupiter, which is not practical for everyday applications.
Room temperature superconductors enable loss- and lean energy transfer, more efficient maglevs, and cheaper and more ubiquitous use of MRI technology. The practical uses of room temperature superconductors are endless. Physicists need to understand how superconductors work at room temperature and what the “Goldilocks” materials that enable superconductivity are.
What is a superconductor? | Live science
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