AsianScientist (Feb. 1, 2012) – Physicists at the University of New South Wales have observed a new kind of interaction that can arise between electrons in a single-atom silicon transistor.
“We have been able to study some of the most complicated transport mechanisms that can arise up to the single atom level,” said lead author Dr. Giuseppe C. Tettamanzi, from the School of Physics at UNSW.
The findings, published this week in the journal Physical Review Letters, in collaboration with scientists from the ICMM in Madrid and the Kavli Institute in The Netherlands, describe how a single electron bound to a dopant atom in a silicon matrix can interact with many electrons throughout the transistor.
In these geometries, electron-electron interactions can be dominated by something called the Kondo effect, considered one of the most complex phenomena found in solid-state physics, said Tettamanzi. Conventionally, this arises from the spin degree of freedom, which represents an angular momentum intrinsic to each electron and is always in the up or in the down state.
However, researchers also observed that similar interactions could arise through the orbital degree of freedom of the electron. This describes the wave-like function of an electron and can be used to help determine an electrons’ probable location around the atom’s nucleus.
Importantly, by applying a strong magnetic field, the researchers were able to tune this effect to eliminate the spin-spin interactions while preserving the orbital-orbital interactions.
The results indicate that quantum electronics could be driven by the orbital nature of electrons, and not just the spin or the charge as was previously thought, Tettamanzi said, which opens the door for a new type of electronics to be explored.
“By tuning the effect in two different symmetries of the fundamental state of the system… we have observed a symmetry crossover identical to those seen in high-energy physics,” said Tettamanzi.
“In our case this crossover was observed simply by using a semiconductor device which is not too different from the transistor you use daily to send your emails.”
The article can be found at: Tettamanzi GC et al. (2012) Magnetic Field Probing of an SU(4) Kondo Resonance in a Single Atom Transistor.
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Source: UNSW; Photo: Lawrence Ratner/Flickr.
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