Regensburg 2013 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 9: Quantum Liquids, Miscellaneous 1

TT 9.6: Talk

Monday, March 11, 2013, 10:45–11:00, H21

Kinetic equations for a system of parametrically excited magnons — •Andreas Rückriegel and Peter Kopietz — Institut für Theoretische Pysik, Universität Frankfurt

Using the functional integral formulation of the Keldysh technique, we derive kinetic equations for the normal and anomalous momentum distribution functions of a system of parametrically excited magnons with two-body interaction in contact with a thermal phonon bath. We then use the results of self-consistent mean field theory to obtain an effective kinetic equation of the Boltzmann type without particle number conservation. Close to thermal equilibrium, we can use a Kramers-Moyal expansion to replace the integral equation by a differential equation which has the form of a continuity equation with an explicit particle number conservation breaking source term. We use our theory to study the thermalization of magnons in the magnetic insulator yttrium-iron garnet.