Origin of the repulsive Casimir force in giant polarization-interconversion materials

TL;DR

This paper investigates how giant polarization interconversion in gyrotropic materials like Weyl semi-metals can lead to strong repulsive Casimir forces, with implications for micro- and nano-electromechanical systems.

Contribution

It identifies the conditions under which repulsive Casimir forces occur in gyrotropic media using Lifshitz theory, highlighting the role of polarization interconversion in these phenomena.

Findings

Repulsive Casimir forces can be achieved in gyrotropic media.

Giant polarization interconversion is the key origin of repulsion.

Weyl semi-metals exhibit strong gyrotropy leading to repulsive forces.

Abstract

Achieving strong repulsive Casimir forces through engineered coatings can pave the way for micro- and nano-electromechanical applications where adhesive forces currently cause reliability issues. Here, we exploit Lifshitz theory to identify the requirements for repulsive Casimir forces in gyrotropic media for two limiting cases (ultra-strong gyroelectric and non-gyroelectric). We show that the origin of repulsive force in media with strong gyrotropy such as Weyl semi-metals arises from the giant interconversion of polarization of vacuum fluctuations.