Casimir effect in twisted photonic gratings with in-plane chirality

Abstract: We investigate the Casimir effect in a system of two twisted photonic gratings made of uniaxially anisotropic materials. Two distinct configuretions are explored: a stack of symmetric gratings and a stack of in-plane chiral gratings, with the latter realized by choosing specific orientaton of anisotropy axis relative to stripes. We apply the reflection-matrix-based Casimir Lifshitzformalism to explore hoe twiat angle, material anisotropy, and the separation between gratings influence Casimir energy, force and torque. Our calculations reveal that the equilibrium orientation of the gratings is governed by the anisotropy rotation angles, leading to a chiral configuration where the anisotropy axes of the upper and lower gratings are mutually parallel. These findings demonstrate that material anisotropy provids a pwerful mechanism for controlling rotational alignment forces in nanophotonic system.