Proximity Phenomena in van der Waals Heterostructures

Sergio O. Valenzuela, Catalan Institution for Research and Advanced Studies

January 21, 2022

The isolation of a large variety of two-dimensional materials (2DM) and their co-integration in van der Waals heterostructures has opened new avenues for innovative material design and engineering. In particular, the structural interface quality in the atomically smooth 2DMs has led to alternative and versatile strategies beyond simply combining materials functionalities. Indeed, properties of interest, such as magnetism, superconductivity or spin-orbit interaction, can be imprinted in a chosen 2DM by proximity-induced effects [1]. Such an approach is compelling for spintronic devices, which harness their functionality from thin layers of magnetic and non-magnetic materials and their interfaces [1]. In this talk, I will introduce fundamental concepts on proximity effects and then present recent experiments in which we investigate the spin dynamics in graphene-transition metal dichalcogenides heterostructures. I will show that the spin-orbit coupling in graphene can be strongly enhanced by proximity effects. As a consequence, the spin relaxation becomes highly anisotropic, with spin lifetimes that are markedly different depending on the spin orientation [2,3]. I will further demonstrate that the proximity-induced spin-orbit coupling leads to strongly enhanced spin-to-charge interconversion [4]. By performing spin precession experiments in appropriately designed Hall bars, we are able to separate the contributions of the spin Hall and the spin galvanic effects. Remarkably, their corresponding conversion efficiencies can be tailored by electrostatic gating in magnitude and sign, peaking near the graphene charge neutrality point and having a large magnitude even at room temperature.