Accessing Ultrafast Spin-Transport Dynamics in Copper Using Broadband Terahertz Spectroscopy
Jiří Jechumtál, Reza Rouzegar, Oliver Gueckstock, Christian Denker, W Hoppe, Quentin Remy, Tom S. Seifert, Peter Kubaščík, Georg Woltersdorf, Piet W. Brouwer, Markus Münzenberg, Tobias Kampfrath, Lukáš Nádvorník
Abstract
We study the spatiotemporal dynamics of ultrafast electron spin transport across nanometer-thick copper layers using ultrabroadband terahertz emission spectroscopy. Our analysis of temporal delays, broadening, and attenuation of the spin-current pulse reveals ballisticlike propagation of the pulse peak, approaching the Fermi velocity, and diffusive features including a significant velocity dispersion. A comparison to the frequency-dependent Fick's law identifies the diffusion-dominated transport regime for distances >2 nm. These findings lay the groundwork for designing future broadband spintronic devices.