Non-Adiabatic Quantum Molecular Dynamics Study of Photo-Induced Three-Stage Picosecond Amorphization in Low Temperature SrTiO₃

Photoexcitation can drastically modify material potential energy surfaces, allowing access to hidden phases. SrTiO₃ (STO) is an ideal material for photoexcitation study due to its prevalent use in nanostructured devices and rich range of functionality-changing lattice motions. Recently, a hidden ferroelectric phase in STO was accessed through weak THz excitation of polarization-inducing phonon modes. In contrast, while strong excitation was shown to induce nanostructures on STO surfaces and control nanopolarization patterns in STO-based heterostructures, the dynamic pathways underlying these optically induced structural changes remain unknown. Here, nonadiabatic quantum molecular dynamics reveals picosecond amorphization in photoexcited STO at temperatures as low as 10 K. The three-stage pathway involves photoinduced charge transfer and optical phonon activation, followed by nonlinear charge and lattice dynamics that ultimately lead to amorphization. This atomistic understanding could guide not only laser nanostructuring of STO, but also broader “quantum materials on demand” technology.