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

The physical properties of chiral crystals are inherently tied to their structural handedness, making external control of chirality a key challenge for functional materials design. 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.