On the generality of the LLG equation to the optical limit: an optically-induced helicity dependent torque emerging from the LLG equation

Benjamin Assouline; Amir Capua

doi:10.1117/12.3022485

11 June 2024 On the generality of the LLG equation to the optical limit: an optically-induced helicity dependent torque emerging from the LLG equation

Benjamin Assouline, Amir Capua

Author Affiliations +

Proceedings Volume PC12992, Advances in Ultrafast Condensed Phase Physics IV; PC129920L (2024) https://doi.org/10.1117/12.3022485
Event: SPIE Photonics Europe, 2024, Strasbourg, France

Abstract

It is well known that the Gilbert relaxation time of a magnetic moment scales inversely with the magnitude of the externally applied field, H, and the Gilbert damping, α. Therefore, in ultrashort optical pulses, where H can temporarily be large, the Gilbert relaxation time can momentarily be extremely short, reaching even picosecond timescales. Here we show that for typical ultrashort pulses, the magnetization can respond within the optical cycle such that the optical control of the magnetization emerges by merely considering the optical magnetic field in the Landau-Lifshitz-Gilbert (LLG) equation. Interestingly, when circularly polarized optical pulses are introduced to the LLG equation, an optically induced helicity-dependent torque result. We find that the strength of the interaction is determined by η=αγH/f_opt, where f_opt and γ are the optical frequency and gyromagnetic ratio. Our results illustrate the generality of the LLG equation to the optical limit and the pivotal role of the Gilbert damping in the general interaction between optical magnetic fields and spins in solids.

Conference Presentation

Citation Download Citation

Benjamin Assouline and Amir Capua "On the generality of the LLG equation to the optical limit: an optically-induced helicity dependent torque emerging from the LLG equation", Proc. SPIE PC12992, Advances in Ultrafast Condensed Phase Physics IV, PC129920L (11 June 2024); https://doi.org/10.1117/12.3022485

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