Gate-controlled charge-doping of a Mott insulator in Graphene/α-RuCl3 Heterostructures*

The layered antiferromagnetic Mott insulator α-RuCl3 exhibits many phenomena consistent with the existence of a Kitaev quantum spin liquid. While most works on α-RuCl3 so far have focused on pristine bulk samples, this material can be readily exfoliated down to monolayer thicknesses. Here we study the electronic transport of van der Waals heterostructure devices containing thin a-RuCl3 flakes in contact with monolayer graphene Hall bars. We find an anomalously large conductivity implying the RuCl3 has become charge-doped and is now conducting. The Hall coefficient data show a sharp increase in the density of the second conducting band (in the a-RuCl3) as graphene is gated from hole- to electron-doped. Additionally, the resistivity at low temperature shows clear signals associated with magnetic phase transitions at temperatures 2-3 times higher than the native antiferromagnetic transition in a-RuCl3.