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Double Qdots Control Kondo Effect

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ATHENS, Ohio, Sept. 15, 2006 -- Two quantum dots connected by wires could help scientists better control the Kondo effect in experiments and could lead to a better understanding of structures such as superconductors, according to a new study.

The Kondo effect occurs when electrons become trapped around the magnetic impurities in semiconductor materials, which prompts the electrons to change their spin. This phenomenon has intrigued scientists, as electronic correlations can create interesting and complex behavior in materials.KondoDots.jpg
Nanoscale metallic electrodes (in yellow) can be used to confine electrons in small regions, forming quantum dots. Two quantum dots connected to each other form a double quantum dot. In this case, one of the dots is in the Kondo state, in which the magnetic moment of the confined electron (large red arrow) is compensated (“screened”) by the magnetic moment of surrounding electrons, resulting in a zero net magnetic moment for the entire system. (Illustration: Luis Dias/Ohio University)
In the new work, by Ohio University (OU) and University of Florida physicists and published in a recent issue of Physical Review Letters, scientists demonstrate how the two quantum dot system can behave in two different and interesting ways: As a simile for a Kondo-effect system where one quantum dot is used to "filter" the effect of the current leads, and as a way to study "pseudo-gapped" systems and correlations in them, which can help scientists understand structures such as superconductors.

"This last part is of great current interest to theorists and experimentalists who are exploring what are called quantum phase transitions, which are changes in systems that alter their behavior dramatically as a function of some parameter while remaining at zero (or very low) temperature," said Sergio Ulloa, a professor of physics and astronomy at OU.

The study, funded by the National Science Foundation, was conducted by Luis Dias da Silva, Nancy Sandler and Ulloa, all members of the OU Nanoscale and Quantum Phenomena Institute, and Kevin Ingersent of the University of Florida.

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Sep 2006
The scientific observation of celestial radiation that has reached the vicinity of Earth, and the interpretation of these observations to determine the characteristics of the extraterrestrial bodies and phenomena that have emitted the radiation.
quantum dots
Also known as QDs. Nanocrystals of semiconductor materials that fluoresce when excited by external light sources, primarily in narrow visible and near-infrared regions; they are commonly used as alternatives to organic dyes.
astronomyBasic ScienceelectronsKondo EffectNews & FeaturesOhio Universityquantum dotssuperconductorsUlloaUniversity of Florida

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