IBM Scientists Unlock the Secret of the Kondo Effect

San Jose, CA .-Scientists at the IBM Almaden Research Center in San Jose, CA have forged a breakthrough in understanding an intriguing phenomenon in fundamental physics: the Kondo effect. They report their findings today in the scientific journal Nature Physics.

The Kondo effect, one of the few examples in physics where many particles collectively behave as one object (a single quantum-mechanical body), has intrigued scientists around the world for decades. Now, using a technique that was developed by the same team in 2007, the IBM researchers have shown, for the first time anywhere, that it is possible to predict when the Kondo effect will occur – and to understand why.
The key turns out to be in the geometry of a magnetic atom’s immediate surroundings. By carefully studying how this geometry influences the magnetic moment (or “spin”) of the atom, the emergence of the Kondo effect can now be predicted and understood. This result represents a major advancement in fundamental physics.

The achievement is one of the latest in IBM’s more than two decades of nanotechnology leadership and exploration of the world of magnetism at the atomic scale. Starting with the invention of the Scanning Tunneling Microscope (STM) in 1981, IBM has been at the forefront of research aimed at expanding our abilities to investigate and manipulate individual atoms.

A look at the Kondo Effect
When a single magnetic atom is located inside a metal, the free electrons of the metal ‘screen’ the atom. That way, a cloud of many electrons around the atom becomes magnetized. Sometimes, if the metal is cooled down to very low temperatures, the atomic spin enters a so-called ‘quantum superposition’ state. In this state its north-pole points in two opposite directions at the same time. As a result, the entire electron cloud around the spin will also be simultaneously magnetized in two directions.