Real-Time Modeling of Skyrmion Dynamics in Arbitrary 2D Spatially Dependent Pinning Potential Landscapes

Abstract: Non-flat energy landscapes leading to localized pinning of skyrmions pose an inherent and unavoidable challenge for studies of fundamental 2D spin structure dynamics as well as applications. Accounting for pinning is a key requirement for predictive modeling of skyrmion systems, as it impacts the systems' dynamics and introduces randomizing effects. In this article, we use magneto-optical Kerr microscopy to image skyrmions in a magnetic thin film system in real time and analyze their hopping dynamics within the non-flat energy landscape. To achieve a fully quantitative model, we utilize skyrmion diffusion and dwell times at pinning sites to extrapolate the pinning energy landscape into regions that cannot be sampled on reasonable experimental time scales. For evaluation with a coarse-grained Thiele model, we perform long-time measurements of skyrmion diffusion and then develop a two-step procedure to determine simulation parameters by comparing them to experimentally accessible behavior. This provides a direct conversion between simulation and experimental units, which is the missing key step that has previously prevented quantitative quasiparticle modeling. We demonstrate the predictive power of our approach by measuring the experimentally unexplored density dependence of skyrmion diffusion and show that it is in excellent agreement with simulation predictions. Our technique thus enables quantitative skyrmion simulations on experimental time and length scales, allowing for predictive in-silico prototyping of skyrmion devices.