Hidden chiral signatures in ferroaxial K2Zr(PO4)2
We use first-principles calculations and multipole analyses to demonstrate the relationship between ferroaxiality and chirality in the prototypical ferroaxial material K2Zr(PO4)2. Using the atomic-site electric toroidal monopole as a measure of electronic chirality in real space, we show that, while the paraxial phase of K2Zr(PO4)2 is non-chiral, the ferroaxial phase is antiferro-chiral. By applying an electric field, we induce a ferri-chiral state with net electronic chirality which is opposite for opposite underlying ferroaxial domains and can be tuned by the direction and strength of the electric field. Associated with the real-space induced chirality, we find a distinct response in momentum space, with induced non-zero components in the Berry curvature dipole tensor that switch sign between opposite ferri-chiral domains. Our findings therefore reveal hidden chirality in ferroaxial materials in both real and momentum space.