Dynamics of an Active Nanoparticle in an Optical Trap
Falko Schmidt, Hana Sipova-Jungova, Mikael Käll, Alois Würger, Giovanni Volpe
Friedrich Schiller University Jena, Germany
3 September 2021, 14:00-14.20
Active matter systems in non-equilibrium conditions have recently gained great interest from many disci- plines. Probing the dynamics of active Brownian particles (ABPs) under confinement gives insight into their non-equilibrium processes. Although previous studies have shown the effect of confinement on ABPs on microscale and macroscale, investigating dynamics on the nanoscale remains challenging where thermal fluctuations typically prevail. Here, we investigate experimentally and theoretically a nanoparticle inside an optical trap and driven away from equilib- rium by self-induced concentration gradients. We find the nanoparticle to perform fast orbital rotations away from the trap center and its probability density shift- ing from a Gaussian to a skewed distribution (Fig. 1). Furthermore, we show that by transfer of spin angular momentum from the trapping beam the direction of the particle’s rotation can be controlled. We develop a theoretical model of this system which reveals that the driving mechanism of such fast rotation is the particle’s non-sphericity providing insight for the develop- ment of future nanoscopic engines.