Time: Thursday, October 25th, 9:00
Speaker: Davide BOSSINI, Dortmund
Magnetism in solid state materials is one of the most widely investigated phenomena in condensed matter physics. The conventional description of a magnetic material is formulated in the framework of thermodynamics, since it relies on the concept of equilibrium. While this approach is effective for the ground state properties, its application to the dynamical regime is limited to to spin dynamics with characteristic timescales in which the adiabatic approximation can still be invoked. The technical progresses of pulsed laser sources have provided the possibility to generate intense laser pulses with duration in the 10-100 femtosecond range. Such laser pulses are among the shortest stimuli in contemporary solid state physics. They provide the groundbreaking possibility to drive and detect spin dynamics in magnetic materials in real-time experiments, whose time-resolution is comparable to or even shorter than the two main magnetic interactions, i.e. the spin-orbit coupling and the exchange interaction. Note that aside from the clear academic interest, investigating the optical control of spins on ever-shorter timescales may have relevant implications for possible future developments of the magnetic recording industry. In this talk I will present the basic concepts, methods and goals of the field called “ultrafast magnetism”[1]. In particular, I aim at demonstrating the potentiality and wide applicability of the optical methods, by describing the major breakthroughs reported in this research area. Spectacular phenomena have already been observed, such as the ultrafast demagnetisation[2], the picosecond-deterministic reversal of the magnetisation[3], the coherent control collective spin excitations[4] and even the photo-induced magnetic phase transitions on the picosecond timescale[5]. In the last part of my talk, I plan to discuss the most recent trends[6,7] and some possible future directions.
[1] A. Kirilyuk et al. Rev. Mod. Phys. 82, 2731 (2010)[2] E. Beaurepaire et al. PRL 76, 4250 (1996)
[3] C. Stanciu et al. PRL 99, 047601 (2007)
[4] A.V. Kimel et al Nature 435, 655 (2005)
[5] D. Afanasiev et al. PRL 116, 097401 (2016)
[6] D. Bossini et al. Nat. Comm. 7, 10645 (2016)
[7] D. Bossini et a. Nat. Phys. 14, 370 (2018)