Novel possibility for gyrotropic materials: Incommensurate insulators

Abstract A discussion is presented as to how optical activity can arise from the nature of incommensurately modulated systems. It is demonstrated, on the basis of molecular dynamics simulations, that these have an intrinsic tendency to assume chiral forms with net helicity. It is also pointed out that this tendency has to be explicitly included in theoretical studies, as it is incompatible with periodic boundary conditions.