Smalltalks "Ultrafast Entropy Production by Magnons"

Abstract

Modern technology demands rapid nanoscale material manipulation, highlighting the need to understand non-equilibrium behavior on fundamental scales. While thermodynamic principles have shaped macroscopic machines, translating them to the (sub)picosecond timescale of material excitations drives the emergent field of ultrafast thermodynamics. This talk shows an example of the successful application of thermodynamics to ultrafast phenomena – the definition of entropy production by magnetic degrees of freedom in pump-probe experiments. In our theoretical approach, we consider a ferromagnet excited by a terahertz laser, which we can describe with the stochastic Langevin equation. Using tools from stochastic thermodynamics, we define entropy production and estimate the heat production by magnetic degrees of freedom. In addition, we simulate the dependency of the magnetization dynamics and therefore entropy production on the pump laser. This allows us to predict and guide experiments and further development of nanotechnology which includes magnetic degrees of freedom.