The subject of research belongs to the class of superconductors that become superconducting when
However, these so-called high temperaturesuperconductors are still not fully understood. "Their microscopic excitations and dynamics are necessary to understand superconductivity, but after 30 years of research, many questions still remain open," says Riccardo Comin, assistant professor of physics at MIT.
In 2015, scientists discovered a new specieshigh-temperature superconductor: a sheet of iron selenide only one atomic layer thick, capable of superconducting at a temperature of -208.15 degrees Celsius. In contrast, massive samples of the same material superconduct at a much lower temperature (-265.15 degrees Celsius). The discovery sparked a flurry of investigations.
In an ordinary metal, electrons behave the same waylike individuals dancing in a room. In a superconducting metal, electrons move in pairs, like pairs in a dance. And all of these pairs move in unison, as if they were part of quantum choreography, which ultimately led to the creation of a kind of electronic superfluid.
Scientists have known for a long time that in ordinaryIn superconductors, the "glue" that holds electrons together is formed by the movement of atoms within the material. “If you look at a solid sitting on a table, it looks like it’s not doing anything,” Comin says. However, a lot is happening at the nanoscale. Inside this material, electrons fly in all possible directions, and atoms rattle; they vibrate. In conventional superconductors, electrons use the energy stored in the movement of an atom to form pairs.
The "glue" behind the bonding of electrons intohigh temperature superconductors, other. Scientists have suggested that it is associated with a specific property of electrons - spin. "Rotation can be viewed as an elementary magnet," says Jonathan Pelliciari, an assistant physicist at Brookhaven National Laboratory. The idea is that in a high-temperature superconductor, electrons can take some of the energy from these spins. And this energy is the "glue" that they use to create a pair.
Until now, most physicists thought thatit is impossible to detect or measure spin excitations in a material that is only an atomic layer thick. But physicists not only discovered spin excitations, but, among other things, they also showed that the spin dynamics in an ultrathin sample is dramatically different from the spin dynamics in a massive sample. In particular, the energy of fluctuating spins in an ultrathin sample was much higher - four or five times - than the energy of spins in a massive sample. A resonant inelastic X-ray scattering (RIXS) instrument was used for the study.
“This is the first experimental evidence of spin excitations in an atomically thin material,” says Pelliciari.
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