Ultrafast laser-induced carrier and magnetization dynamics in SrTiO₃ from real-time time-dependent DFT

Recent experimental studies indicate electric-field-driven ferroelectricity [1] and multiferroicity [2] in the paradigmatic nonmagnetic band insulator SrTiO₃ in the terahertz regime. Following a comprehensive study of the optical [3] and x-ray absorption [4] spectra including quasiparticle and excitonic effects, here we explore the response of SrTiO₃ to laser excitation. Using real-time time-dependent density functional theory (RT-TDDFT) as implemented in the Elk code, we investigate both linear and circular polarized laser pulses and vary systematically their frequency and fluence. A complex site- and orbital-dependent temporal dynamics is observed with opposite sign of fluctuations at O and Ti sites and charge transfer from O 2p to Ti 3d states for linearly polarized light, that breaks dynamically inversion symmetry. Notably, circularly polarized pulses induce a finite transient magnetic moment of up to 0.1 μ_B per formula unit which is absent for linearly polarized light. We assess the origin of the induced magnetization.



[1] T.F. Nova et al., Science 364, 1075 (2019)

[2] M. Basini et al., Nature 628, 534 (2024).

[3] V. Begum, M.E. Gruner and R. Pentcheva, Phys. Rev. Mater. 3, 065004 (2019).

[4] V. Begum-Hudde et al., Phys. Rev. Res. 5, 013199 (2023).