Thermoelectrics: Charge Kondo Effect Improves Efficiency
January 19, 2012
Computer processors are made up of ever smaller components; at the same time, their clock speeds are on the rise. This leads to the generation of progressively more heat which must be transported away efficiently to ensure that the processor functions optimally. Thermoelectric materials, which produce temperature gradients when conducting electricity, could be of use here if a way could be found to improve their efficiency.
New scientific findings from physicists in Jülich could help in the development of more efficient thermoelectric materials on the nanoscale. Researchers have been able to demonstrate that the physical phenomenon of the “charge Kondo effect“ improves the thermoelectric properties of quantum dots enormously.
Quantum dots are small areas made of semiconducting material embedded within another semiconductor. Due to their tiny dimensions, quantum mechanical effects occur in them, producing novel material properties. Quantum dots can easily be embedded into electrically-driven semiconductor diode structures and are scalable. This makes them attractive in terms of information technology applications.
Furthermore, the researchers introduced a material in which the charge Kondo effect, previously only theoretically predicted, could be observed for the first time: the semiconductor material lead telluride doped with thallium. They found that doping at a minimum of 0.3 % resulted in degenerate energy levels. Pairs of electrons can then fluctuate and induce the desired effect, along the lines of the more well-known spin Kondo effect, whereby magnetic spins are seen to flip.
The results are available in two current articles in the scientific journals “Physical Review Letters“ and “Physical Review B – Rapid Communications“.
T. A. Costi and V. Zlatic, Phys. Rev. Lett. 108, 036402 (2012), DOI: 10.1103/PhysRevLett.108.036402
S. Andergassen, T. A. Costi, V. Zlatic, Phys. Rev. B 84, 241107 (2011), DOI: 10.1103/PhysRevB.84.241107
Peter Grünberg Institut-2: Theoretical Nanoelectronics
Research group “Strong correlations and mesoscopic physics“ at RWTH Aachen