Superconductors are one of the most interesting materials discovered in the last century. It is used to build medical tomographs, crucial details of particle accelerators, and quantum computers. However, even a hundred years after the discovery of superconductivity, we understand its microscopic mechanisms only in the simplest cases.
Recent findings have suggested that electrons may be quadrupled, and a physicist at the Royal Institute of Technology at KTH, Egor Babaev, has just published the first experimental evidence for this quadrupled effect and the mechanism by which this state occurs. Of the mattery. Their results have been published in the journal Nature Physics.
In their work, Egor Babaev and his team presented evidence that the fermion quadruples in a series of experimental measurements on the iron-based material, Ba1 – xKxFe2As2. The results take place almost 20 years after Babaev first predicted this type of phenomenon, and eight years after he published an article that predicts that it could occur in such material.
What enables the quantum state of superconductivity is electron pairing, which is the technology used in magnetic resonance scanners and quantum computing. The superconductor as a new state of matter is born when the currents of pairs of electrons are no longer dispersed by defects and obstacles and a conductor can lose all electrical resistance.
It occurs within a material as a result of the bonding of two electrons rather than repelling each other, as they would in a vacuum. This phenomenon earned Leon Cooper, John Bardeen, and John Schrieffer the Nobel Prize in Physics in 1972.
Of course, the Bardeen-Cooper-Schrieffer theory did not allow the quadruplication state of fermions, such behavior could not occur, so when Babaev’s experimental collaborator at Technische Universtät Dresden, Vadim Grinenko, found in 2018 the first signs of a fermion that quadrupled the condensate, defying years of prevalent scientific agreement.
And it is only in recent years that the theoretical idea of four fermion condensates has been widely accepted.
Several years of experimentation and research in laboratories at multiple institutions were the next steps to validate the finding.
Babaev says that the key among the observations made is that the fermionic quadruple condensates spontaneously break the time reversal symmetry. In physics, time reversal symmetry is a mathematical operation that replaces the expression of time with its negative in formulas or equations to describe an event in which time runs backward or all movements are reversed. If one reverses the direction of time, the fundamental laws of physics still hold.
“However, in the case of a condensate of four fermions that we report, the investment of time puts it in a different state ,” explains the expert. “It will probably take many years of research to fully understand this state. The experiments open up a host of new questions, revealing a host of other unusual properties associated with their reaction to thermal gradients, magnetic fields, and ultrasound that still need to be better understood.
Referencia: “State with spontaneously broken time-reversal symmetry above the superconducting phase transition” by Vadim Grinenko, Daniel Weston, Federico Caglieris, Christoph Wuttke, Christian Hess, Tino Gottschall, Ilaria Maccari, Denis Gorbunov, Sergei Zherlitsyn, Jochen Wosnitza, Andreas Rydh, Kunihiro Kihou, Chul-Ho Lee, Rajib Sarkar, Shanu Dengre, Julien Garaud, Aliaksei Charnukha, Ruben Hühne, Kornelius Nielsch, Bernd Büchner, Hans-Henning Klauss and Egor Babaev, 18 October 2021, Nature Physics.
DOI: 10.1038/s41567-021-01350-9
