Nonresonant holeburning in the Terahertz range: Brownian oscillator model

Abstract

The response to the field sequence of nonresonant hole burning, a pump-wait-probe experiment originally designed to investigate slow relaxation in complex systems, is calculated for a model of Brownian oscillators, thus including inertial effects. In the overdamped regime the model predictions are very similar to those of the purely dissipative stochastic models investigated earlier, including the possibility to discriminate between dynamic homogeneous and heterogeneous relaxation. The case of underdamped oscillations is of particular interest when low-frequency excitations in glassy systems are considered. We show that also in this situation a frequency selective modification of the response should be feasable. This means that it is possible to specifically address various parts of the spectrum. An experimental realization of nonresonant holeburning in the Terahertz regime therefore is expected to shed further light on the nature of the vibrations around the so-called boson peak.

Dynamic Kerr effect responses in the terahertz range

“…We do not show the result, because the expression is lengthy and not instructive, but it shows the correctness of our numerical integrations. The finding that the signal appears mainly at the damping is in contrast to our calculations for nonresonant holeburning [8], where the main signals appeared at the eigenfrequency.…”

“…Here, we assume the same functional behaviour as found for the polarizability correlations, the so-called light-to-vibration-coupling C(ω i ). A detailed discussion of this ansatz is given in [8]. As a consequence we approximately have…”

“…It is valid in this form if the AC-field has been switched on at time t = −∞. However, since we are dealing with nonlinear response functions here, no such relation exists [8] [22]. It is not possible to derive the Kerr effect response to the oscillating field from the pulse response.…”

“…In a recent publication [8], we presented a model to describe an NHB-experiment on a much faster time scale, in the range of inverse Terahertz (THz). These short timescales are experimentally accessible since recent advances in the preparation of ultrashort laserpulses should allow to provide one or several coherent cycles of a sufficiently strong electric field in that frequency range [9].…”

Kerr effect as a tool for the investigation of dynamic heterogeneities

“…If NHB is carried out as outlined in Ref. [31] and the dynamics are treated in a rotational diffusion ansatz as in this work, we find in the homogeneous limit the same expression as Eq. ( 21) up to prefactors and a modified time dependence.…”