Handedness selection and hysteresis of chiral orders in crystals

Abstract

A phase transition can drive the spontaneous emergence of chiral orders in crystals below a critical temperature. However, selecting either a right- or a left-handed phase with the aid of electromagnetic fields is challenging, particularly when intrinsic polar and axial moments are lacking. In this work we show that \textit{purely} chiral phases with opposite handedness, when both deriving from one degenerate instability, are linked by accessible transition states. While these states compete with the chirality under an electromagnetic field, a circularly polarized source can select the handedness of the system. This selection is mediated by a chiral monopole and may further result in a hysteresis process of the gyrotropic properties, namely the optical activity, below the critical temperature. We suggest several materials, among which K${}_3$NiO${}_2$, as candidates for possible experimental observation.