Stuttgart 2012 – wissenschaftliches Programm

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A: Fachverband Atomphysik

A 26: Poster: Atomic systems in external fields

A 26.6: Poster

Mittwoch, 14. März 2012, 16:30–19:00, Poster.V

Double excitations from the solution of the Kadanoff--Baym equations — •Karsten Balzer and Michael Bonitz — Institut für Theoretische Physik und Astrophysik, CAU Kiel, Leibnizstraße 15, 24098 Kiel

In a quantum many--body system, the population of states of double excitation character (doubly excited states) is a clear indicator for correlations importantly contributing to the nonequilibrium dynamics.

In this contribution, we analyze such correlation-induced transitions, being absent in a mean--field Hartree--Fock (HF) treatment, on the basis of the nonequilibrium Green function solving the Kadanoff--Baym equations by direct time--propagation [1]. As test system, we consider a four--electron quantum dot at zero temperature in the regime of moderate--to--strong coupling (see also poster by S. Hermanns [3]). The approximate (HF and second-order Born) absorption spectra are compared to exact diagonalization results where singly, doubly and other multiply excited states are identified by means of the approximate excitation level [2].

[1] K. Balzer, S. Bauch and M. Bonitz, Phys. Rev. A 81, 022510 (2010); ibid. 82, 033427 (2010). [2] J.F. Stanton and R.J. Bartlett, J. Chem. Phys. 98, 7029 (1993). [3] This contribution focuses on the generalized Kadanoff--Baym ansatz.