Spin Transport and Proximity-Induced Magnetism in Graphene-Based van der Waals Structures

Abstract

Spintronics is a promising field to meet the future requirements to information technology. The term describes the use of the spin degree of freedom, a quantum mechanical property, as information carrier. While spin related effects in metallic systems are already used in hard disks for several years, spin-based logic devices are still in an early research stage. The realization of such devices requires the tackling of several experimental challenges such as an efficient manipulation of spins while simultaneously maintaining a long spin lifetime. In metallic and semiconductor films, the spin lifetime is often limited to a few picoseconds at room temperature. On the contrary, graphene is a promising platform for spin-based logic devices due to a relatively weak spin scattering rate and a predicted spin lifetime up to microseconds. Graphene consists of carbon atoms, arranged in a hexagonal lattice and only one atom thick. Given the low intrinsic spin-orbit coupling in carbon, graphene is predicted to provide spin lifetimes several orders of magnitude above typical values for conventional metallic and semiconductor systems. However, the small spin-orbit coupling strength and the lack of a band gap makes the electrical control of spins in graphene rather inefficient. This thesis addresses two current topics of graphene spintronics: the efficient control of spin by inducing magnetism into graphene and the spin transport in fully hBN encapsulated high quality. The high sample quality of encapsulated graphene allows the first measurement of the coupling between the spin and valley degree of freedom in pristine bilayer graphene