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Dirac materials such as graphene and topological insulators (TIs) are known to have unique electronic and spintronic properties. We combine graphene with TIs in van der Waals heterostructures to demonstrate the emergence of a strong proximity-induced spin-orbit coupling in graphene. By performing spin transport and precession measurements supported by ab initio simulations, we discover a strong tunability and suppression of the spin signal and spin lifetime due to the hybridization of graphene and TI electronic bands. The enhanced spin-orbit coupling strength is estimated to be nearly an order of magnitude higher than in pristine graphene. These findings in graphene-TI heterostructures could open interesting opportunities for exploring exotic physical phenomena and new device functionalities governed by topological proximity effects. ; Chalmers researchers acknowledge financial support from the European Union (EU) Horizon 2020 Research and Innovation Programme GrapheneCore2 contract number 785219 (Graphene Flagship), EU FLAG-ERA project (from Swedish Research Council VR no. 2015- 06813), Swedish Research Council VR project grants (no. 2016-03658), Graphene Center, and the AoA Nano program at Chalmers University of Technology. Catalan Institute of Nanoscience and Nanotechnology (ICN2) was supported by the Severo Ochoa program from Spanish Ministry of Economy and Competitiveness (MINECO; grant no. SEV-2013-0295) and funded by the Centres de Recerca de Catalunya Programme/Generalitat de Cataluña. S.R. acknowledges the Spanish MINECO and the European Regional Development Fund (project no. FIS2015- 67767-P MINECO/FEDER), and the Secretaría de Universidades e Investigación del Departamento de Economía y Conocimiento de la Generalitat de Cataluña (2014 SGR 58). ; Peer reviewed

Engineering 2D material heterostructures by combining the best of different materials in one ultimate unit can offer a plethora of opportunities in condensed matter physics. Here, in the van der Waals heterostructures of the ferromagnetic insulator Cr2Ge2Te6 and graphene, our observations indicate an out-of-plane proximity-induced ferromagnetic exchange interaction in graphene. The perpendicular magnetic anisotropy of Cr2Ge2Te6 results in significant modification of the spin transport and precession in graphene, which can be ascribed to the proximity-induced exchange interaction. Furthermore, the observation of a larger lifetime for perpendicular spins in comparison to the in-plane counterpart suggests the creation of a proximity-induced anisotropic spin texture in graphene. Our experimental results and density functional theory calculations open up opportunities for the realization of proximity-induced magnetic interactions and spin filters in 2D material heterostructures and can form the basic building blocks for future spintronic and topological quantum devices. ; Authors from Chalmers, ICN2, and University of Regensburg acknowledge funding from the European Union's Horizon 2020 research and innovation programme under Grant agreement no. 785219 (Graphene Flagship Core 2). The authors at Chalmers acknowledge financial support from EU FlagEra project (from Swedish Research Council VR No. 2015-06813), Swedish Research Council VR project Grants (No. 2016-03658), Graphene center and the AoA Nano program at Chalmers University of Technology. We acknowledge Dr Ron Jansen for useful discussions about proximity-induced exchange and stray Hall effects in the heterostructures. We acknowledge help from Bing Zhao in our group and staff at Nanofabrication laboratory and Quantum device laboratory for useful discussions and help in fabrication and measurements of devices. ICN2 is funded by the CERCA Programme/Generalitat de Catalunya and is supported by the Severo Ochoa program from Spanish MINECO (Grant No. SEV-2017-0706). M. Vila acknowledges funding from 'La Caixa' Foundation. ; Peer reviewed