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

TL;DR

This study reveals that a soft phonon mode can induce a reversible transition between achiral and chiral phases in crystals, controllable by pressure, strain, and electric fields, with potential applications in chiral material design.

Contribution

It introduces a phonon-driven mechanism for reversible chirality in crystals, demonstrated through first-principles calculations on K$_{3}$NiO$_{2}$.

Findings

Structural phase transition mediated by a soft phonon mode.

Electric field can switch the chirality of the crystal.

Pressure and strain control the phase transition.

Abstract

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.