A phonon-driven mechanism for an emergent and reversible chirality in crystals

We demonstrate through first-principles calculations applied to the K$_{3}$NiO$_{2}$ crystal that a structural phase transition from an achiral to a chiral phase can be mediated by a degenerate soft phonon mode and controlled by pressure and epitaxial strain. Breaking such degeneracy with an electric field generates a competition between enantiomorphic, polar, and orthorhombic displacements. Originated by the interaction between spontaneous chiral and induced polar and axial modes, an optimal parameter window for converting the handedness of the system into its opposite kind is observed.