Proximity-induced spin-orbit and exchange coupling in graphene-based heterostructures

Two-dimensional materials (2D) and their van der Waals heterostructures provide unique opportunities for the exploration of various spin-related phenomena that emerge due to their combined properties and functionalities. Spintronic devices operate based on spin, the angular momentum of an electron, which is used to transfer and store information. Apart from the requisite preservation of the spin information over a micro-meter distance, there is a need for active electrical control of the spin signal for efficient spin-logic operations. In this regard, graphene is an excellent choice of material for 2D spintronic devices as it has high charge carrier mobility and weak spin-orbit coupling (SOC), allowing for long-distance spin transport. However, for the electrical generation and/or manipulation of the spin signal, materials with strong spin-orbit or exchange coupling are required. In this thesis, we experimentally show that it is possible to induce both spin-orbit and exchange couplings in graphene by the proximity to other 2D materials. We observe that the induced SOC in graphene in the vicinity of transition metal dichalcogenides results in a strong spin lifetime anisotropy and the emergence of spin-to-charge conversion mechanisms. Furthermore, we detect a strong exchange splitting in graphene in the proximity of a 2D magnetic material, CrSBr, that results in large spin polarization of conductivity. This allows for the active electrical and thermal generation of spin currents by the magnetic graphene itself. These experimental observations open the path for the direct applications of electrically-controlled 2D spintronic and spin-caloritronic circuitries with graphene-based heterostructures.