Giant diffusion of nanomechanical rotors in a tilted washboard potential

TL;DR

This paper experimentally demonstrates giant diffusion enhancement in a nanomechanical rotor within a tilted optical potential, revealing a new platform for studying weak thermal noise effects in rotational diffusion.

Contribution

It introduces an experimental setup for biased optical potentials in the low friction regime, showing giant diffusion enhancement and validating a two-state model based on Langevin dynamics.

Findings

Rotational diffusion coefficient increases over 1000 times with pressure variation.

Experimental results agree with a two-state Langevin model.

System provides a platform for studying weak thermal noise in rotational diffusion.

Abstract

We present an experimental realization of a biased optical periodic potential in the low friction limit. The noise-induced bistability between locked (torsional) and running (spinning) states in the rotational motion of a nanodumbbell is driven by an elliptically polarized light beam tilting the angular potential. By varying the gas pressure around the point of maximum intermittency, the rotational effective diffusion coefficient increases by more than 3 orders of magnitude over free-space diffusion. These experimental results are in agreement with a simple two-state model that is derived from the Langevin equation through using timescale separation. Our work provides a new experimental platform to study the weak thermal noise limit for diffusion in this system.