Non-equilibrium properties of an active nanoparticle in a harmonic potential
Journal article, 2021

Active particles break out of thermodynamic equilibrium thanks to their directed motion, which leads to complex and interesting behaviors in the presence of confining potentials. When dealing with active nanoparticles, however, the overwhelming presence of rotational diffusion hinders directed motion, leading to an increase of their effective temperature, but otherwise masking the effects of self-propulsion. Here, we demonstrate an experimental system where an active nanoparticle immersed in a critical solution and held in an optical harmonic potential features far-from-equilibrium behavior beyond an increase of its effective temperature. When increasing the laser power, we observe a cross-over from a Boltzmann distribution to a non-equilibrium state, where the particle performs fast orbital rotations about the beam axis. These findings are rationalized by solving the Fokker-Planck equation for the particle’s position and orientation in terms of a moment expansion. The proposed self-propulsion mechanism results from the particle’s non-sphericity and the lower critical point of the solution.

Author

Falko Schmidt

University of Gothenburg

Hana Jungová

Chalmers, Physics, Nano and Biophysics

Mikael Käll

Chalmers, Physics, Nano and Biophysics

Alois Würger

University of Bordeaux

Giovanni Volpe

University of Gothenburg

Nature Communications

2041-1723 (ISSN)

Vol. 12 1 1902

Subject Categories

Physical Chemistry

Atom and Molecular Physics and Optics

Other Physics Topics

DOI

10.1038/s41467-021-22187-z

PubMed

33772007

More information

Latest update

4/22/2021