Evidence for charge transfer and proximate magnetism in graphene–α−RuCl3 heterostructures

We report a study of electronic transport in van der Waals heterostructures composed of flakes of the antiferromagnetic Mott insulator <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>α</mi><mtext>–</mtext><msub><mi>RuCl</mi><mn>3</mn></msub></mrow></math> placed on top of monolayer graphene Hall bars. While the zero-field transport shows a strong resemblance to that of isolated graphene, we find a consistently <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>p</mi></math>-type Hall effect suggestive of multiband conduction, along with a nonmonotonic and gate-voltage-dependent excursion of the resistivity at low temperatures that is reminiscent of transport in the presence of a magnetic phase transition. We interpret these data as evidence for charge transfer from graphene to <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>α</mi><mtext>–</mtext><msub><mi>RuCl</mi><mn>3</mn></msub></mrow></math> in an inhomogeneous device yielding both highly and lightly doped regions of graphene, while the latter shows a particular sensitivity to magnetism in the <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>α</mi><mtext>–</mtext><msub><mi>RuCl</mi><mn>3</mn></msub></mrow></math>. Thus proximity to graphene is a means to access magnetic properties of thin layers of magnetic insulators.