Novel Possibility for Gyrotropic Materials: Incommensurate Insulators.

摘要

A discussion is presented as to how optical activity can arise from the nature of incommensurately modulate 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. The property of gyrotropy, the rotation of the direction of polarization of a plane polarized electromagnetic wave, is common to many systems. Specifically, any organic molecules can exist in stereo isomeric forms (e.g. dextrose and lactose) of opposite 'handedness.' In such materials this handedness is intrinsic to the molecules themselves and manifest its presence irrespective of the overall organizational of the molecules (solid, liquid, liquid crystal, etc.). Perhaps more subtle, is the handedness that can be present in an ordered solid composed of single ions or atoms which , lacking internal molecular structure, can have no intrinsic handedness. Keywords: Reprints. (JES)