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DY: Fachverband Dynamik und Statistische Physik
DY 26: Brownian Motion, Transport and Anomalous Diffusion
DY 26.12: Vortrag
Dienstag, 17. März 2020, 13:00–13:15, HÜL 186
Hot Brownian Motion in the Ballistic Timescale — •Xiaoya Su1, Alexander Fischer1, Frank Cichos1, and Klaus Kroy2 — 1Peter Debye Institute for Soft Matter Physics, University Leipzig, Leipzig, Germany — 2Institute of Theoretical Physics, University Leipzig, Leipzig, Germany
Brownian motion is the erratic motion of particles in a fluid due to the bombardment of the particle with solvent molecules providing thermal energy and viscous friction. It is fundamental for the dynamics of soft matter and defines the prototype of a fluctuation dissipation relation. While at long timescales the motion is purely stochastic, it is at shorter times influenced by hydrodynamic effects and even ballistic at ultrashort times. Yet, the ballistic motion is still determined by the temperature of the system. Here we explore the transition to the ballistic regime for a hot Brownian particle, i.e. a microparticle which is heated by a laser in an optical trap. In this case the particle temperature is different from the solvent temperature and so far,only theoretical predictions exist for the relevant temperature determining the particle velocity.
We report the first measurements of the thermal non-equilibrium process in a specially designed optical trap which is able to resolve particle displacements of about 20 pm with a time-resolution of 5ns. We show how the mean squared displacement of the particle from the nanoseconds to the seconds timescale changes as a function of the surface temperature of the particle and discuss the model of a frequency dependent effective temperature of hot Brownian motion.