Researchers from the California Institute of Technology (Caltech) and Yale University in the US have precisely quantified the Kondo effect in a real material using fundamental physics calculations. According to ScienceAlert, the breakthrough, published in the journal Science, marks the first time physicists have calculated the phenomenon directly from basic physical laws rather than relying on lab experiments and simplified models.
What the Kondo Effect Does in Metals
Known to physicists since the 1930s, the Kondo effect describes the unusual interference that magnetic atoms create inside metals. Ordinarily, cooling a metal improves its electrical conductivity because lower energy allows electrons to flow more smoothly.
When a metal contains one or two magnetic atoms as impurities, however, cooling it below a threshold called the Kondo temperature causes electrical resistance to rise again. Electrons swarm around the magnetic impurities, canceling out the atoms' magnetism while simultaneously blocking the flow of electricity.
“That is the signature of the Kondo effect, and it's a property of the electrons in the impurity interacting with the electrons traveling through the bulk metal,” said Caltech physicist Garnet Chan.
While scientists already understood the cause of the phenomenon, modeling it with full precision remained out of reach. Predicting when resistance will flip across different combinations of metals and magnetic impurities involves a complex “many-body problem” where temperatures, electron spins, and magnetism interact at tiny scales beyond the reach of even the most powerful supercomputers.
Borrowing Chemistry Techniques for First-Principles Modeling
To get around those computational limits, the Caltech and Yale team used an ab initio (“from first principles”) approach. They adapted techniques from chemistry to model a single magnetic atom without simplification, treating it as though it were a larger molecule.
Combining mathematical shortcuts with extensive computer time, the team applied the basic laws of quantum physics to the modeled atom and repeated the calculations to refine their predictions. “It is now possible to predict the properties of some complicated materials purely through computation without referring to experiments,” Chan said.
When the researchers compared their computational results against laboratory measurements of the Kondo effect, the new prediction system proved up to 100 times more accurate than current simplified modeling in some cases.
Scaling Up to Superconductors and Quantum Magnets
For this study, the team tested the most basic combinations of metals and magnetic atoms, which Chan described as “a baby step, or a prototype problem, along the way to more complex phenomena such as high-temperature superconductors and quantum magnets.” Because the approach has been shown to work, the researchers can begin scaling it up to study complex quantum materials without needing laboratory data first.
We are in an exciting era in which faithful predictive quantum descriptions of the full chemical complexity of real materials are coming within reach. It is becoming realistic to predict material-specific behavior of correlated electrons from first principles, even in some of the most challenging classes of quantum materials.
Linqing Peng, Chemist, Caltech
More accurate prediction tools can help scientists investigate materials with complex electron behaviors, such as superconductors that could transform power grids and large-scale computing, though the researchers note that significant progress still lies ahead.
This article was written by AI from reporting by sciencealert.com.
