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Calculating time-dependent spectral functions of correlated impurity systems

Jülich, 9 November 2017 – Physicists at Forschungszentrum Jülich have developed a formalism for calculating time-dependent spectral functions of correlated impurity systems. This has a number of applications in topics of current research interest; these range from the fundamental issue of how strongly correlated systems far from equilibrium thermalize at long times after a quench, i.e. a sudden change of a system parameter, to time-dependent quantum transport through quantum dots. When it is implemented within non-equilibrium dynamical mean field theory using supercomputing facilities, it can also be applied in time-dependent pump-probe spectroscopy experiments on strongly correlated materials.

Using the formalism, the researchers succeeded in shedding light on the formation of the so-called Kondo resonance following a quench. This had not been previously explained in detail, even though much was known about the Kondo resonance in equilibrium. The Kondo resonance is a kind of low energy bound state in which the conduction electron spins in a metal arrange themselves in such a way that they cancel out the spin of a magnetic impurity. The phenomenon is ubiquitous in strongly correlated systems, and manifests itself in, for example, nanoscale quantum dots, heavy fermions and in the quasi-particle peak of correlated metals close to the Mott transition.

The Jülich physicists found a "preformed" or "baby" Kondo resonance at very short times following the quench, while it takes much longer for the resonance to fully form. They suggest that the "preformed" Kondo resonance should be observable in the quench dynamics of future cold atom realizations of Kondo impurities in optical lattices.

Photoemission experiments reveal the spectroscopic signature of the Kondo resonance.Photoemission experiments reveal the spectroscopic signature of the Kondo resonance.
Copyright: Phys. Rev. Lett., DOI: 10.1103/PhysRevLett.119.156601

More:

H. T. M. Nghiem, T. A. Costi;
Time Evolution of the Kondo Resonance in Response to a Quench;
Phys. Rev. Lett. 119, 156601 – Published 13 October 2017
DOI: 10.1103/PhysRevLett.119.156601

Peter Grünberg Institute/Institute for Advanced Simulation - Theoretical Nanoelectronics (PGI-2/IAS-3)

Contact:

Theo Costi
Peter Grünberg Institute/Institute for Advanced Simulation - Theoretical Nanoelectronics (PGI-2/IAS-3)
Phone +492461 61-4246
Email: t.costi@fz-juelich.de

Press contact:

Angela Wenzik, Science journalist
Forschungszentrum Jülich,
Phone +492461 61-6048
Email: a.wenzik@fz-juelich.de


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