Strong and tunable anisotropy in monolayer graphene with broken symmetry

Abstract

Low-symmetry two-dimensional materials have attracted much attention in recent years due to their exotic and incredible properties. Here, we construct Ta2NiS5-based van der Waals heterostructures to introduce in-plane polarization in monolayer graphene through symmetry engineering. Angle-dependent conductance and mobility measurement combined with theoretical calculations all verify that the pristine Ta2NiS5 possesses prominent electrical anisotropy, with anisotropic ratio (a-axis/c-axis) of about 2.1 in conductivity and 3.28 in mobility. Furthermore, we demonstrate that van der Waals interlayer coupling has induced explicit in-plane polarization in monolayer graphene according to angle-dependent Raman spectroscopy and electrical transport measurement on monolayer-graphene/Ta2NiS5 heterostructures. In polarized graphene, the conductivity and mobility ratios are up to 3.21 and 4.84, respectively. The induced polarization in monolayer graphene within heterostructures probably originates from strain, lattice reconstruction, induced symmetry reduction and charge transfer through van der Waals interfaces. These results might provide inspiration to study symmetry-related van der Waals heterostructures and pave their way to novel nano-electronic devices.