Abstract-Simulation of hot-carrier dynamics and terahertz emission in laser-excited metallic bilayers

Dennis M. Nenno, Rolf Binder, and Hans Christian Schneider

https://journals.aps.org/prapplied/accepted/b007cA03Me01fb05a16544b0f877e00f6cbc75e8e

We present a multiscale model that simulates optically induced spin-currents in metallic bilayer structures that emit terahertz (THz) radiation after optical pulse excitation. We describe hot-electron transport in metallic bilayer by a Boltzmann transport equation, which is solved numerically using a particle-in-cell approach. Optical excitation and propagation effects are taken into account by determining the emitted THz waves from the excited carrier dynamics. We apply this approach to an Fe/Pt bilayer and show in detail how microscopic scattering effects and transport determine the emitted signal. The versatility of the approach presented here allows it to be readily adapted to a wide spectrum of spintronic THz emitter designs. As an example, we show how the THz generation efficiency, defined as output to input power ratio, can be improved and optimized using serially stacked layers in conjunction with THz anti-reflection coatings. We derive an analytical expression for the THz emission of a single layer that allows us to determine the relationship between emitted field and current profile that generates it.