The new magnetic phenomenon, which has not been observed before, may have significant implications for our understanding of the field of unconventional superconductivity, explains physicist Ray Osborn, in an article published long ago in the scientific journal Nature Communications.
![A neutron diffraction image showing the scattering results from a barium-iron-arsenide sample that includes sodium ions attached to 24% of the barium sites. 2nd order symmetry exists below a temperature of 90K but 4th order symmetry returns at a temperature below 40K. The resulting atomic and magnetic structures are shown on the right side of the figure, where the blue circles represent iron atoms, and the red arrows represent the direction of their magnetic momentum. [Courtesy of Jared Allred / Argonne National Laboratory].](https://www.hayadan.org.il/images/content3/2014/06/super_conductor-500x342.jpg)
Dr. Moshe Nahamani
Scientists from the US National Laboratory (Argonne) discovered an unknown phenomenon (phase) among a family of superconducting materials called iron arsenides, a phenomenon that could be used for the efficient supply of energy in a wide variety of new technologies.
The discovery sheds light on the controversy concerning the interrelationships between atoms and electrons responsible for the unusual superconductivity of these materials. The new magnetic phenomenon, which has not been observed before, may have significant implications for our understanding of the field of unconventional superconductivity, explains physicist Ray Osborn, in an article published long ago in the scientific journal Nature Communications.
Superconducting materials are able to transmit electric current without encountering resistance, this is compared to superconductors such as the copper wires used in most electric cables that lose their energy during the transmission of the electric current. Superconducting materials are still not used today to conduct electricity in the normal grid lines since they need to be cooled to extremely low temperatures. However, a special range of "unconventional superconducting" materials may provide this capability. The researchers believe that by understanding the theory underlying the activity of these special materials, it is possible to raise the temperature at which they currently work, and thus they will be able to use these materials in a wide variety of new technologies.
The theory behind older conventional superconductors is quite solid and structured - pairs of electrons, which normally repel each other, connect to each other through the distortion of the surrounding atoms and can thus move through the metal (in a normal conducting material, these electrons would be detached from the atoms while creating Heat). In unconventional conductors the electrons still form pairs, but researchers still don't know what connects them. In order to reach a state where the electrons in a superconductor flow freely without restrictions, these materials require a lot of persuasion. The iron arsenides used by the researchers are normally magnetic, but when sodium is added to them, the magnetism disappears and the materials eventually become superconducting materials at the low temperature of minus 240 degrees Celsius. The magnetic nature of the material also affects the atomic structure - at room temperature, the iron atoms form a square lattice with 4th order symmetry, but when they are cooled below the magnetic threshold temperature, the lattice distorts to form a rectangular structure with only 2nd order symmetry ("nematic order"). It was common to think that this symmetry is maintained until the material becomes a superconductor, but the new finding contradicts this.
The team of researchers discovered a phenomenon where the material returns to its square shape with 4th order symmetry, instead of 2nd order, close to the transition point to becoming a superconductor. This can be predicted with the help of a neutron powder diffraction method, which is a sensitive and accurate method, but is carried out in a small number of places in the world. With this method it is possible to measure not only the different positions of the atoms in space, but also the directions of the microscopic magnetic momentum of each of them.
The discovery of the new phenomenon may help resolve a long-standing dispute regarding the origin of order 2 symmetry. Theoreticians have debated over the years whether this symmetry is caused by magnetism or by the way the orbitals are arranged. The orbital explanation claims that electrons tend to be in certain d orbitals, thus moving the lattice towards 2nd order symmetry. Magnetic models, on the other hand, suggest that magnetic interactions are responsible for creating the 2nd order symmetry and that they themselves are the key to the very existence of the superconducting state. It is possible that the factor that connects the two electrons together in iron arsenide-type superconductor pairs is magnetism. Theories based on the orbital factor do not predict a return to fourth-order symmetry at this point, explains the lead researcher, but the magnetic models do. To date, this result has only been observed experimentally in those compounds that include the sodium salt in their content, but the researchers believe that the finding provides confirmation for the magnetism model in general materials of the iron arsenide type. The new finding could also contribute to our understanding of superconductivity in other types of materials, such as copper oxides, in which 4nd order symmetry was also observed.
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The amount of talk on Kim does not indicate the quality. I wander through NATURE and find myself enriched by the knowledge written on your website about the material there. The articles from there are very interesting to me. The general explanation in the article is nice. Regarding electron pairs that move together. The phenomenon is also fascinating. How does the total electron population produce a chemical bonding twin in pairs. Including fascinating quantum thermodynamics. The connection started by Leib Davidovich Landau between quantum theory and statistical physics occupies a huge part in modern physics.
Maybe I will listen to lectures for free, because I am in another faculty, and also work, and also have a family, but I really want to master the method. I have the books on the subject, but listening to a course or researching the subject is a different level.
The relevant article. Too sharp defamation will lead to an unjustified depreciation of Dr. Nachmani's articles, God forbid.
There is a mistake in the translation in the spirit of things, and you understand better. Here I would go to Wikipedia and look up what it is. There really is true value there.
Nachmani is a strong bridge to nature articles in nanotechnology and physics, physical chemistry.
Without such a bridge, the site presents many discoveries in Israel, but the scope is more limited, Israel is not the center of the world.
Moshe is not the only one presenting from the outside, but one of the most important.
Seriously, this is supposed to be a science site? The article says something about neutron powder, a concept that even science fiction would be ashamed to use. The translation of neutron powder diffraction to neutron powder interference shows a basic lack of understanding. Neutrons are subatomic particles found in the nucleus that cannot be made into powder. When it says neutron powder diffraction, it means that you take a powder of the material on which you want to perform neutron diffraction (using the wave property of the neutron to determine the structure of the material). The fact that the substance is in powder apparently makes it difficult to get distinct interference bands from its crystallographic structure and therefore only a small number of places can use this method.