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DY: Fachverband Dynamik und Statistische Physik

DY 1: Quantum Dynamics, Decoherence and Quantum Information I

DY 1.4: Talk

Monday, March 11, 2013, 10:15–10:30, H39

General Decoupling Procedure for Expectation Values of Four-Operator Products in Electron-Phonon Quantum Kinetics — •Nicolas Teeny and Manfred Fähnle — Max Planck Institute for Intelligent Systems, 70569 Stuttgart, Heisenbergstr.3,Germany

Electron-phonon quantum kinetic effects are important for studying the coherent ultrafast dynamics on time scales shorter than about a picosecond after exciting the electrons of a solid with a short laser pulse of duration smaller than 100 femtoseconds. An example is the femtosecond-demagnetization of a ferromagnetic film after exposure to a strong optical laser pulse. In the density-matrix formalism of electron phonon quantum kinetics the hierarchy of infinitely many coupled equations of motion for the expectation values of products of electron and phonon creation and annihilation operators of arbitrary order is usually terminated on the level of equations of motion for the expectation vales of three-operator products by using decoupling procedures for the four-operator products occurring in these equations. In the literature decoupling procedures are discussed for special types of electron and phonon states. In the talk generalized decoupling procedures are derived for arbitrary electron and phonon states.