  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.
