Thermal Effects in the Casimir Torque between Birefringent Plates

TL;DR

This paper studies how thermal fluctuations affect the Casimir torque between birefringent plates, revealing significant reductions and altered angular behavior, which could enable temperature-controlled nanoscale devices.

Contribution

First analysis of thermal effects on Casimir torque between birefringent plates, showing temperature-dependent torque reduction and reversal possibilities.

Findings

Thermal fluctuations reduce Casimir torque by up to 100 times.

Temperature alters the torque's angular dependence from sinusoidal.

Dissimilar plates can reverse torque direction with temperature changes.

Abstract

The Casimir effect, originating from quantum and thermal fluctuations, is well known for inducing forces between closely spaced surfaces. When these surfaces are optically anisotropic, these interactions can produce a Casimir torque that rotates the surfaces relative to each other. We investigate, for the first time, the influence of thermal fluctuations on the Casimir torque between birefringent plates. Our results reveal that thermal modes significantly diminish the torque, with reductions up to 2 orders of magnitude for highly birefringent materials. Temperature is also shown to alter the angular dependence of the torque, significantly deviating from the typical sinusoidal behavior, and becomes particularly important at large separations that exceed the thermal wavelength. Finally, we demonstrate that systems of dissimilar birefringent plates that exhibit a distance-dependent reversal in the torque's direction can enable precise control of the torque's magnitude and sign through temperature manipulation. These findings advance our understanding of quantum and thermal fluctuation interplay and provide a framework for designing innovative nanoscale sensors and devices leveraging Casimir torque phenomena.