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arXiv · 2602.20693

Disentangling the dynamics of transient spin and orbital magnetization in SrTiO$_3$ via the inverse Faraday effect from RT-TDDFT

Andri Darmawan·Markus E. Gruner·Rossitza Pentcheva
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Abstract

Motivated by recent evidence of ferroelectricity and even multiferroicity in the prototypical diamagnetic band insulator SrTiO$_3$ from terahertz experiments, we investigate the carrier and magnetization dynamics of SrTiO$_3$ excited optically by linearly (LPL) and circularly polarized light (CPL). Our RT-TDDFT simulations show a pronounced site- and orbital-dependent charge transfer from O$2p$ to Ti $3d$ states. With LPL anti-phase oscillations of the electron-density lobes at O and Ti resemble the soft transverse optical phonon mode and break dynamically inversion symmetry. CPL instead drives a coherent rotation of the charge dipoles around oxygen, producing a helicity-dependent transient magnetization of opposite sign at O and Ti, even without ionic motion. The dominant effect stems from the transfer of angular momentum (AM) from light to the electronic orbital AM, while spin-orbit coupling plays a key role in the transfer from orbital to spin AM, the former being an order of magnitude larger than the latter. The real-time resolution allows us to disentangle the inverse Faraday effect, which follows the pulse envelope, from optical orientation, which builds up during the pulse and saturates afterwards. The results demonstrate that purely electronic processes without lattice motion induce ultrafast magnetisation in a non magnetic insulator, offering a tunable route for light controlled magnetic functionalities.

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Andri Darmawan, Markus E. Gruner, Rossitza Pentcheva. 2026-02-24. Disentangling the dynamics of transient spin and orbital magnetization in SrTiO$_3$ via the inverse Faraday effect from RT-TDDFT. https://arxiv.org/abs/2602.20693

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