Estudio de los efectos del confinamiento, interferencia y reflexión parcial del espín en grafeno de alta calidad mediante análisis de curvas de precesión

Abstract

CONDITION FOR PROJECT PUBLICATION. Spin transport in graphene has attracted significant interest in spintronics due to the long spin diffusion lengths and spin relaxation times observed even at room temperature. The experimental extraction of these parameters is commonly based on fitting Hanle spin precession curves measured in the non-local geometry, which are traditionally interpreted using models that assume an infinitely long transport channel. However, in high-quality graphene devices with finite-length channels, where the channel length is comparable to or shorter than the spin diffusion length, these assumptions are no longer valid. In this work, the effects of spin confinement, interference, and partial spin reflection in finite-length graphene channels are analyzed through the fitting of Hanle spin precession curves. An extension of the analytical solution of the Bloch equation is employed, explicitly incorporating geometric effects associated with spin reflection at the channel ends and interference between multiple reflected spin trajectories. The transport parameters obtained from this extended model are compared with those extracted using the conventional fitting approach. The results demonstrate that the traditional analysis can lead to significant discrepancies in the extraction of the spin relaxation time, diffusion coefficient, and spin diffusion length when geometric effects are not taken into account. In particular, an overestimation of the spin relaxation time is observed in the strong confinement regime. Additionally, the possible transition to a zero-dimensional spin transport regime is analyzed when the device length is much smaller than the spin diffusion length, characterized by a nearly uniform spatial distribution of the spin chemical potential and a Lorentzian response of the Hanle curves. This work highlights the importance of explicitly considering confinement and partial reflection effects for a physically consistent interpretation of spin transport in graphene. Keywords: Graphene spintronics, Hanle spin precession, Spin confinement, Spin interference and reflection.