Photostriction-Driven Phase Transition in Layered Chiral NbOX₂ Crystals: Electrical-Field-Controlled Enantiomer Selectivity

Chiral crystals offer an unique platform for controlling structural handedness through external stimuli. However, the ability to select between structural enantiomers remains challenging, both theoretically and experimentally. In this work, we demonstrate a two-step pathway for enantiomer selectivity in layered chiral NbOX₂  (X = Cl, Br, I) crystals based on photostriction-driven phase transitions. Ab-initio simulations reveal that optical excitation is capable of inducing a structural phase transition in NbOX₂ from the monoclinic (C2) ground state to the higher-symmetry (C2/m) structure. In the resulting transient high-symmetry state, an applied electric field breaks the residual inversion-symmetry degeneracy, selectively stabilizing one enantiomeric final state configuration over the other. Our results establish a combined optical-electrical control scheme for chiral materials, enabling reversible and non-contact enantiomer selection with potential applications in ultrafast switching, optoelectronics, and chiral information storage.