Mid-infrared light control of ferroaxial order

Materials that exhibit structural ferroaxial order hold potential for novel multiferroic applications. However, in pure ferroaxials, domains are not directly coupled to stress or static electric field due to their symmetry, limiting the ability to pole the crystal and switch between domains. Here we propose a general optical approach to transiently excite single-domain ferroaxial order from a high-symmetry non-ferroaxial phase. We show that circularly polarized light pulses on resonance with selected infrared-active phonons dynamically induce helicity-controlled single-domain ferroaxial order. Nonlinear contributions to the polarizability play an essential role in this phenomenon. We illustrate the feasibility of our approach using the prototypical ferroaxial material RbFe(MoO₄)₂. Our first-principle calculations and dynamical simulations show a fluence threshold, beyond which noticeable single-domain ferroaxial order is induced. We further discuss our results in the context of future pump-probe optical experiments.