Physicists tailor magnetic pairings in nanoscale semiconductors

Electrons love to zip around metals such as copper, especially if the metal is cooled to temperatures near absolute zero. But if they encounter a magnetic atom (say, iron) during their travels, the electrons will try to "screen," or cancel out, the magnetic atom's spin alignment by pairing with it. This pairing modifies the flow of electrons in the metal, in a phenomenon called the Kondo effect.

But what if there weren't just one set of mobile electrons zipping around the metal? What if there were two, and both sets fought equally hard to couple with the magnetic impurity atom? Torn between two lovers, the magnetic atom couldn't decide with which set to partner. The competition would go unresolved, and the atom would join neither, instead existing in a remarkable state of frustrated independence known as the two-channel Kondo state.

n the March 8 issue of Nature, researchers at Stanford, Harvard and Israel's Weizmann Institute of Science reported that they have built such a system in a semiconductor nanostructure. By applying voltages to nanoscale electrodes, the scientists can tune how strongly the magnetic atom couples to one set of electrons, or channel, compared to the other set. Their system of correlated electrons demonstrates a two-channel Kondo effect.

http://www.brightsurf.com/news/headlines/29352/Physicists_tailor_magnetic_pairings_in_nanoscale_semiconductors.html