Nonlinear quantum dynamics of SrTiO₃ under ultrafast laser pump

Recent advancements in laser technology have made it possible to observe the real-time dynamics of atomic nuclei on a femtosecond scale. Strontium titanate (SrTiO₃) is an interesting example of a quantum paraelectric material, known for its near-ferroelectric transition at low temperatures, which is affected by quantum nuclear fluctuations. In this study, we conduct first-principles simulations of the time-resolved quantum nuclear dynamics of SrTiO₃ when exposed to pulsed terahertz (THz) radiation, specifically targeting the mode associated with ferroelectricity. Our innovative approach, based entirely on first principles and without any adjustable parameter[1,2], effectively reproduces the unique excitation pathways identified in time-resolved X-ray signals, including the upconversion of energy from low-frequency to high-frequency phonons[3] and the out-of-equilibrium stress induced on the sample by the laser pulse.

[1] L Monacelli, F Mauri, Phys Rev B 103, 104305 (2021)

[2] F Libbi, A Johansson, L Monacelli, B Kozinsky, Atomistic simulations of out-of-equilibrium quantum nuclear dynamics, arXiv:240800902, 2024

[3] M Kozina et al., Nature Physic 15, 397 (2019)