Physicists model the Kondo effect in metals more accurately — ScienceAlert

Researchers at the California Institute of Technology and Yale University in the United States have developed a method that makes it possible to calculate the Kondo effect in a real material with high accuracy based on the fundamental laws of physics. The results of the work were published in the journal Science, ScienceAlert reports.

What is the Kondo effect

Normally, when a metal is cooled, its electrical resistance decreases because electrons can move more freely. However, the presence of magnetic impurity atoms changes this relationship: below a certain temperature, known as the Kondo temperature, resistance begins to rise again.

This effect arises from the interaction of electrons moving through the metal with the electrons of a magnetic impurity. Electrons accumulate around the impurity, screen its magnetism and at the same time impede the flow of electric current. California Institute of Technology physicist Garnet Chan noted that this interaction is precisely the defining feature of the Kondo effect.

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Calculations from first principles

Accurately modeling this process is difficult because of the so-called many-body problem: at extremely small scales, temperature, electron spins and magnetism interact simultaneously. Previously, researchers relied on laboratory measurements and simplified models to estimate the effect.

The new method uses an ab initio approach, meaning calculations from first principles. The authors borrowed methods from chemistry that made it possible to describe a single magnetic atom in greater detail as a more complex molecular system, and then repeatedly applied quantum-physics calculations with mathematical reductions.

Accuracy and further research

A comparison of the calculations with laboratory measurements confirmed the method's accuracy. In some cases, it was 100 times more accurate than existing simplified models. At the first stage, the team studied the simplest combinations of metals and magnetic atoms. In the future, this approach may help study more complex quantum materials, including high-temperature superconductors and quantum magnets.