Lateral-drag Casimir forces induced by anisotropy

TL;DR

This paper predicts a novel lateral Casimir force caused by electromagnetic fluctuations near anisotropic surfaces, which could enable nanoparticle manipulation without relative motion of bodies.

Contribution

It introduces the concept of lateral Casimir forces induced solely by anisotropy, expanding understanding of fluctuation-induced forces in hyperbolic materials.

Findings

Lateral drag forces arise from electromagnetic field fluctuations near anisotropic slabs.

The force direction depends on the anisotropy axis orientation.

Potential applications in nanoparticle manipulation without surface movement.

Abstract

We predict the existence of lateral drag forces near the flat surface of an absorbing slab of an anisotropic material. The forces originate from the fluctuations of the electromagnetic field, when the anisotropy axis of the material forms a certain angle with the surface. In this situation, the spatial spectra of the fluctuating electromagnetic fields becomes asymmetric, different for positive and negative transverse wave vectors components. Differently from the case of van der Waals interactions in which the forward-backward symmetry is broken due to the particle movement or in quantum noncontact friction where it is caused by the mutual motion of the bodies, in our case the lateral motion results merely from the anisotropy of the slab. This new effect, of particular significance in hyperbolic materials, could be used for the manipulation of nanoparticles.