RS Fellow - EPSRC grant (2014): Mitigating spin-current relaxation in spin-orbit coupled graphene: towards spin current routing in 2D carbon

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Graphene has opened a new chapter in solid-state physics due its fascinating electronic properties and high potential for innovative applications in domains as diverse as flexible electronics and solar cells. One aspect of graphene research that is currently attracting much attention is in the control of a fundamental property of electrons known as spin. This dictates that an electron is always in one of two possible states, either 'up' or 'down', meaning that the electron itself could provide the basis for a binary logic bit ('0' or '1'). Devices based on such a concept promise faster processing speeds with less energy consumption than current charge-based technologies. However, the practical realisation of spin-based transistors awaits emergent nanomaterials enabling efficient manipulation of the spin state of charge currents. Graphene is one of the most promising candidates due to the fact that it entirely consists of a 2D network of carbon that is only one atom thick. This feature leads to extreme surface sensitivity and the possibility to very precisely tailor electronic, chemical, and magnetic properties through, for example, adsorption of atomic species (adatoms). We have recently predicted that adatoms leading to local enhancement of the spin-orbit coupling in graphene can drive the formation of macroscopic spin currents in the absence of magnetic fields, a phenomenon known as the spin Hall effect. An outstanding question is concerned with the main spin relaxation mechanisms that limit the lifetimes of spin signals generated through the spin Hall effect in adatom-decorated graphene. This theoretical project will employ a broad scope approach, combining analytical tools and a novel method for fully quantum transport simulations with billions of atoms, to uncover adatom decorations incorporating both robust spin current generation and spin coherence over relevant time scales. The latter is a crucial step towards the implementation of spin logic functions necessary to explore the recently discovered spin Hall effect.