Nonequilibrium quantum dynamics in SrTiO<sub>3</sub> under impulsive THz radiation with machine learning.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 40938991.
- Also identified by DOI 10.1126/sciadv.adw1634 and PMC identifier 13141898.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Ultrafast spectroscopy paved the way for probing transient states of matter produced through photoexcitation. The microscopic processes governing the formation of these states remain largely unknown, due to the inherent challenges in accessing the microscopic behavior of materials, which is strongly influenced by nuclear quantum effects. Here, we perform simulations of quantum nuclear dynamics in the nonequilibrium regime, extending beyond the current state of the art. By combining first-principles simulations with machine learning, we unveil the complex quantum dynamics of SrTiO<sub>3</sub> emerging after terahertz laser pumping. We disclose the microscopic origin of the phonon upconversion, observed experimentally but not fully understood, and quantify the lifetime of the out-of-equilibrium motion, which is beyond the reach of the state-of-the-art simplified models. Crucially, our simulations predict that terahertz pump pulses can generate persistent out-of-equilibrium stress capable of inducing polar order. This work lays the foundation for systematic explorations of complex quantum materials sensitive to photoexcitation.