Handedness Selection and Hysteresis of Chiral Orders in Crystals

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 Letter, we show that 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.