Dresden 2020 – scientific programme

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MA: Fachverband Magnetismus

MA 63: Spin: Transport, Orbitronics and Hall Effects III

MA 63.8: Talk

Friday, March 20, 2020, 11:30–11:45, HSZ 403

Spin dynamics driven by optical spin-orbit torque — •Ritwik Mondal, Andreas Donges, and Ulrich Nowak — Department of Physics, Universität Konstanz, Konstanz 78464, Germany

Interest in controlling spins by means of ultra-short light pulses has grown immensely due to its potential technological applications. To this end, several light-spin interaction effects can contribute to the spin dynamics, e.g., the nonrelativistic Zeeman effect. However, the relativistic light-spin coupling effects cannot be neglected if the laser power is higher. In this case, a spin precession occurs due to an additional optical spin-orbit torque (OSOT) [1]. It is believed that the OSOT originates from the relativistic spin-orbit coupling of excited non-equilibrium photo carriers that is independent of the helicity of the laser pulse [1]. Here, we examine the existence of an OSOT, a relativistic spin torque originating from the spin-orbit coupling of the applied field with the magnetic spins [2]. Our analytical calculations show that the OSOT depends on the helicity of the light and proportional to the intensity, while inversely proportional to the frequency. We compare the effects of the nonrelativistic Zeeman torque and the relativistic OSOT for magnetic systems excited by a circularly polarised laser pulse. Our results show that the optical spin-orbit torque could exert torques on the spins comparable to the Zeeman torque.
[1] N. Tesarova et. al. Nature Photonics 7, 492 (2013)
[2] R. Mondal et. al. Phys. Rev. B 92, 100402(R) (2015)