Friday, 18 March, 2011
Kondo effect lights up
NIM publication highlighted in Physical Review Letters
The Kondo problem - the interaction between an impurity spin and a surrounding sea of conduction electrons - has been first observed in the 1930s and attracted renewed interest with its realization in quantum dots.
In the current issue of Physical Review Letters, the group of NIM member Jan von Delft and colleagues in the US and Europe present calculations that ask: How does the many-body Kondo state evolve when the interaction is turned on (or off) rapidly with light? The publication is highlighted in the "Synoses" part of the journal.
The authors assume a semiconductor quantum dot coupled, by tunneling contacts, to a Fermionic reservoir. Initially, the electrons on the quantum dot have a net spin of zero, but laser light tuned to the right frequency can excite an electron into the conduction band of the quantum dot that interacts with the electrons in the reservoir.
The ability to rapidly turn the Kondo effect on with light offers a unique way to explore the so-called Anderson orthogonality catastrophe—a prediction about how violently the quantum many-body state of the electronic reservoir changes in response to a sudden change in the scattering potential (in this case, the spin). Signatures of this “catastrophe” are visible in the tails of the optical absorption line shape and, according to Türeci et al.’s calculations, should be tunable with a magnetic field (Source: Jessica Thomas, PhysRevLett).
Many-Body Dynamics of Exciton Creation in a Quantum Dot by Optical Absorption: A Quantum Quench towards Kondo Correlations. Hakan E. Türeci, M. Hanl, M. Claassen, A. Weichselbaum, T. Hecht, B. Braunecker, A. Govorov, L. Glazman, A. Imamoglu, and J. von Delft