Repulsive Casimir force between Weyl semimetals

TL;DR

This paper investigates the Casimir force between Weyl semimetals, revealing conditions under which the force can be tuned from attractive to repulsive using material properties and external parameters.

Contribution

It demonstrates that Weyl semimetals can exhibit a tunable Casimir force, including repulsive interactions, by adjusting thickness, magnetic field, and chemical potential.

Findings

Casimir force is repulsive at short range for idealized semi-infinite Weyl semimetals.

Finite thickness reduces long-range attraction, enabling repulsion at all distances in thin films.

External parameters like magnetic field and chemical potential can control the force's magnitude and sign.

Abstract

Weyl semimetals are a class of topological materials that exhibit a bulk Hall effect due to time-reversal symmetry breaking. We show that for the idealized semi-infinite case, the Casimir force between two identical Weyl semimetals is repulsive at short range and attractive at long range. Considering plates of finite thickness, we can reduce the size of the long-range attraction even making it repulsive for all distances when thin enough. In the thin-film limit, we study the appearance of an attractive Casimir force at shorter distances due to the longitudinal conductivity. Magnetic field, thickness, and chemical potential provide tunable nobs for this effect, controlling the Casimir force: whether it is attractive or repulsive, the magnitude of the effect, and the positions and existence of a trap and antitrap.