Berlin 2018 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 84: Glasses and Glas transition (joint session DY/CPP)

CPP 84.2: Vortrag

Freitag, 16. März 2018, 10:15–10:30, BH-N 334

Nonlinear response theory: simple stochastic models — •Gregor Diezemann — Institut für Physikalische Chemie, Universität Mainz

The effect of large electric fields on the relaxation of supercooled liquids and also other systems like ionic liquids and crystals has been studied intensively during the last decade. Due to the formal lack of an analogue to the well known fluctuation dissipation theorem valid for linear response, one essentially relies on model calculations in the nonlinear case. There are a number of different models that have been used to compute the nonlinear response of glassforming systems, such as the so-called box model, the model of isotropic dipole reorientations or the dipole flips in an asymmetric double well potential (ADWP). I will discuss the results of model calculations of the nonlinear response for simple stochastic models for the dynamics. In particular, I will consider the ADWP model which is known to exhibit a peak in the modulus of the third-order response in a narrow temperature range around some characteristic temperature. Interestingly, in fifth order one observes peaks in the modulus around two characteristic temperatures. These peaks are related to the vanishing of the nonlinear static susceptibility in the respective order. The results will be discussed in the light of recent experimental observations.