The strange behavior of a superconducting metal at high temperatures

Metal superconducting at high temperatures

phenomenon electrical connection In metallurgy it has been well known to physicists for many years. Temperature is also known to affect metals in several ways. For example, an increase in temperature increases the electrical resistance of a metal and a decrease in temperature reduces it. This is because when the temperature rises, the electrons have more kinetic energy and therefore move faster and more randomly. This is the phenomenon of resistance.

An increase in temperature in ferromagnetic metals such as iron, cobalt, and nickel reduces the magnetization of these metals. If the temperature exceeds a certain limit, the metal completely loses its magnetism. This threshold is called the “Curie temperature.”

In recent years, another class of minerals has received increasing attention from scientists: copper. They are metals that behave differently, especially with regard to phenomena related to electricity.

Among the latter, it will now be necessary to add the new metallic substance, which the team of physicists discovered at the origin of this new study, published in temper nature. This substance with strange metallic behavior consists of a mixed mixture of barium oxide, copper, and yttrium, which YBCO noted for its simplicity. This “multi” metal has been known for some time for its superconducting properties at elevated temperatures.

When we talk about temperature rise in the context of superconductivity, we must understand that it is neither hot nor very high. exactly the contrary ! “Classical” superconductivity occurs at temperatures close to absolute zero, that is -273.15 ° C. Metals like copper are superconductors at temperatures of 77 K, or -196.15 degrees Celsius, which stays very cold, but rather “hot” in terms of superconductivity.

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Cooper pairs, strange associations

When an electric current is made to rotate in metallic materials of the copper family, electricity does not flow thanks to the electrons, but thanks to the particles of the boson family, the Cooper pairs.

A Cooper pair is a bond between two electrons that, at a given moment, find themselves in certain conditions favoring the pairing of two electrons of negative electric charge, albeit identical. In metal, Cooper pairs can “slide” over each other and with the entire atomic lattice without offering any resistance.

The composition of the Cooper pair in the metal can be explained simply as follows. Normally, the electron in the metal behaves and moves like a free particle. The electrons repel each other because they have an identical negative electric charge. On the other hand, they attract positive ions to the solid metallic lattice. It is a strong attraction that can distort this lattice and cause it to get closer to the electron. Then the positive charge attracts other electrons. If the energy of attraction is greater than the energy of the electrons repulsion, then they combine to form the Cooper pair.

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Strange behavior in the bosonian system

Cooper pairs act like bosons and thus follow different “rules” than electrons which are fermions. Cuprates, which contain Cooper pairs, adopt superconducting behaviour, and thus conduct electricity without any resistance at temperatures much higher than those of conventional superconductors.

What caught the researchers’ attention is that even when they reach the critical temperature for superconductivity, cuprates continue their strange metallic behavior.

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In ordinary metals, the resistance increases with temperature, but only up to a certain threshold. When this threshold is exceeded, the resistance becomes constant according to the Fermi fluid theory. This can be explained by the fact that the electrons circulating in the metal collide with the vibrating metal atomic structure at a certain temperature and scatter.

On the other hand, in cuprates, the resistance increases with temperature in a linear manner without encountering a threshold where it becomes stable. Scientists now have to try to understand why the coppers behave in this way. This understanding opens the way for many applications in electrical networks or computing as engineers are constantly trying to reduce energy losses.

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