Attosecond magnetization dynamics in non-magnetic materials driven by intense femtosecond lasers

TL;DR

This paper predicts that intense femtosecond lasers can induce attosecond-scale magnetization dynamics in non-magnetic materials through nonlinear spin-flipping processes, enabling ultrafast control of magnetic states.

Contribution

It introduces a novel theoretical prediction of ultrafast, non-perturbative spin dynamics in non-magnetic materials driven by strong laser fields, mediated by multi-photon and spin-orbit interactions.

Findings

Non-magnetic materials can transiently become magnetic via nonlinear spin-flipping.

Magnetization oscillates on ~500 attoseconds even with linearly polarized light.

Speed of magnetization control can be tuned by laser wavelength and intensity.

Abstract

Irradiating solids with ultrashort laser pulses is known to initiate femtosecond timescale magnetization dynamics. However, sub-femtosecond spin dynamics have not yet been observed or predicted. Here, we explore ultrafast light-driven spin dynamics in a highly non-resonant strong-field regime. Through state-of-the-art ab-initio calculations, we predict that a non-magnetic material can be transiently transformed into a magnetic one via dynamical extremely nonlinear spin-flipping processes, which occur on attosecond timescales and are mediated by a combination of multi-photon and spin-orbit interactions. These are non-perturbative non-resonant analogues to the inverse Faraday effect that build up from cycle-to-cycle as electrons gain angular momentum. Remarkably, we show that even for linearly polarized driving, where one does not intuitively expect any magnetic response, the magnetization transiently oscillates as the system interacts with light. This oscillating response is enabled by transverse anomalous light-driven currents in the solid, and typically occurs on timescales of ~500 attoseconds. We further demonstrate that the speed of magnetization can be controlled by tuning the laser wavelength and intensity. An experimental set-up capable of measuring these dynamics through pump-probe transient absorption spectroscopy is outlined and simulated. Our results pave the way for new regimes of ultrafast manipulation of magnetism.