Casimir torque between corrugated metallic plates

TL;DR

This paper calculates the Casimir torque between corrugated metallic plates considering realistic effects, showing the torque can be significant and measurable at micrometer separations.

Contribution

It provides a detailed scattering approach calculation of Casimir torque including finite conductivity and polarization effects, improving upon the proximity force approximation.

Findings

Casimir torque arises from misaligned corrugated plates.

Proximity force approximation overestimates the torque by a factor of 2.

The torque could be experimentally measured at separations up to 1 μm.

Abstract

We consider two parallel corrugated plates and show that a Casimir torque arises when the corrugation directions are not aligned. We follow the scattering approach and calculate the Casimir energy up to second order in the corrugation amplitudes, taking into account nonspecular reflections, polarization mixing and the finite conductivity of the metals. We compare our results with the proximity force approximation, which overestimates the torque by a factor 2 when taking the conditions that optimize the effect. We argue that the Casimir torque could be measured for separation distances as large as 1 $\mu{\rm m}.$