Regensburg 2022 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe

DY: Fachverband Dynamik und Statistische Physik

DY 3: Statistical Physics far from Thermal Equilibrium

DY 3.7: Vortrag

Montag, 5. September 2022, 11:45–12:00, H18

Barrier crossing in a viscoelastic bath — •Félix Ginot¹, Juliana Caspers², Matthias Krüger², and Clemens Bechinger¹ — ¹Fachbereich Physiks Universität Konstanz, 78457 Konstanz, Germany — ²Georg-August Universität Göttingen, 37073 Göttingen, Germany

The activated, i.e., fluctuation-assisted hopping of a Brownian particle across an energy barrier Δ U is a fundamental process with important applications across science, such as in chemical reactions, protein folding, or drug absorption. Such processes can be rationalized using Kramers theory, which predicts the hopping rate ν ∝ exp(−Δ U/k_BT) with k_BT the thermal energy, in agreement with experimental observations. Many systems, however, cannot be described in terms of a single degree of freedom, notably when memory effects need to be taken into account. In this work we experimentally investigate barrier crossing of a Brownian particle in a double-well potential suspended in a viscoelastic solvent which exhibits non-Markovian behavior, i.e., memory. For potential barriers up to several k_BT we find the hopping dynamics to be characterized not by a single but by two time scales which can differ by more than two orders of magnitude. While the long time scale increases exponentially with Δ U (as in Kramers theory), the short one is almost unaffected by the barrier height. The latter results from elastic energy fluctuations of the viscoelastic bath due to excitations arising from the particle’s hopping motion. Our results, which are in agreement with a simple model where the fluid is described as a Maxwell medium, have immediate consequences for the above examples, e.g., altering the interpretation and prediction of lifetimes.