Scientists at Caltech and Yale University have developed a way to precisely calculate the Kondo effect in specific real materials, something that had not previously been possible. For decades, researchers have largely depended on simplified models that capture the phenomenon only approximately. The new approach instead works directly from a material's true atomic and electronic structure.
The advance could help pave the way for realistic computer simulations of more complicated quantum materials, including high-temperature superconductors. In these materials, the behavior of any one electron is strongly influenced by what nearby electrons are doing, making the system difficult to describe with conventional approximations. The researchers report their method and findings in a paper published in Science.
The lead authors are Linqing Peng (PhD '25) and Tianyu Zhu of Yale University. Both Peng and Zhu began working on the project in the laboratory of Garnet Chan, Bren Professor of Chemistry and director of the Rudolph A. Marcus Center for Theoretical Chemistry at Caltech.
"It is now possible to predict the properties of some complicated materials purely through computation without referring to experiment," says Chan, who is the senior author of the paper and a Simons Investigator in Physics. "These first materials that we have studied are like a baby step, or a prototype problem, along the way to more complex phenomena such as high-temperature superconductors and quantum magnets." The Kondo Effect -- A Classic Many-Body Challenge In many materials used in modern electronics, including semiconductors such as silicon, interactions among electrons are weak enough that they can often be ignored when describing the material's overall behavior. That is not true for strongly correlated materials, which are important for many proposed quantum technologies.
In those systems, understanding how electrons influence and scatter from one another is essential. The Kondo effect appears in one of the simplest examples of a strongly correlated system. It occurs when a single magnetic atom, such as iron or manganese, is placed as an impurity inside a metal such as copper.
When the material is cooled below a particular temperature (known as the Kondo temperature), its electrical behavior changes in an unusual way. Ordinarily, cooling a metal causes its electrical resistance to fall steadily, allowing current to flow more easily. But in a metal containing a magnetic impurity, resistance stops falling when the Kondo temperature is reached.
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