Physicists have confirmed the first observations of four-electron coupling. This quadruple is a physical state that is predicted in advance and can provide information about Superconductivity, the special circumstances in which a material can transmit electricity without resistance.
The results will be published in the journal Natural physics.
In the superconducting state, the electrons are paired, which leads to unusual macroscopic properties. Electrons should simply repel each other, but under certain conditions – low temperatures and in crystals – they can combine. And when they do, they can flow unhindered by mistakes and obstacles. The material is now a superconductor and has no electrical resistance.
Some scientists wonder if it is possible to produce quadruplets as well. This idea runs counter to the expectations of the Bardeen-Cooper-Schrieffer (BSC) theory, which underlies the microscopic understanding of superconductivity. For this to happen, something must prevent the formation of an electron pair and then allow the formation of a quadruple.
In 2018, the team discovered strange behavior in the material indicating such a rare condition. Further research in several institutions and laboratories confirms this and is published this week.
The material is a mixture of barium, potassium, iron and arsenic. Its chemical formula is Ba1 xKxFe2As2 and if you are familiar with chemical formulas, you may be surprised to find a letter x there. It just points to a variable – scientists can play around with how much barium and potassium they consume.
And that’s the key to this discovery. The material is usually superconducting (under a certain temperature) but when x 0.8 suddenly instead of seeing superconductivity, they see the opposite.
The decisive proof that the probability of electron formation is quadrupled is the breaking of the time-reversal symmetry. If the reversal of time is not disturbed while observing a state, it will look the same as time flowing forward or backward. This happens in superconductors.
“In the case of the four fermion condensate we reported, however, the time reversal puts it in a different state,” said senior author Professor Egor Babaev of the KTH Royal Institute of Technology in a statement. opinion.
“It will likely take years to fully understand this condition,” he said. “The experiment opened up a number of new questions and revealed a number of other unusual properties associated with its response to thermal gradients, magnetic fields and ultrasound.” it should be understood better.”
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