  Electrical generation and detection of pure spin currents without the need of
magnetic materials are key elements for the realization of full electrically
controlled spintronic devices. In this framework, achieving a large
spin-to-charge conversion signal is crucial, since considerable outputs are
needed for plausible applications. Unfortunately, the values obtained so far
have been rather low. Here we exploit the spin Hall effect by using Pt, a
non-magnetic metal with strong spin-orbit coupling, to generate and detect pure
spin currents in a few-layer graphene channel. Furthermore, the outstanding
properties of graphene, with long distance spin transport and higher electrical
resistivity than metals, allows us to achieve in our graphene/Pt lateral
heterostructures the largest spin-to-charge voltage signal at room temperature
reported so far in the literature. Our approach opens up exciting opportunities
towards the implementation of spin-orbit-based logic circuits and all
electrical control of spin information without magnetic field.
