Transport anisotropy of one-dimensional graphene superlattice induced by periodic ferroelectric domains*

We investigate the transport anisotropy in one-dimensional (1D) graphene superlattice (GSL) induced by prepatterned periodic domains in a ferroelectric bottom gate. We work with 50 nm single crystalline ferroelectric Pb(Zr,Ti)O₃ (PZT) films deposited on (La,Sr)MnO₃ buffered SrTiO₃ substrates. Periodic polarization up (P_up) and down (P_down) stripe domains are patterned on PZT using conductive atomic force microscopy. The domain periodicity varies from 200 nm to 266 nm. We then transfer hBN-graphene stacks onto the pre-patterned domains and fabricate them into top-gated FET devices. The difference in carrier density between the two polarization regions reaches around 3×10¹³ cm^-2 at 2 K due to the pyroelectric effect. For the 1D GSL with current perpendicular to the stripe domains, the hBN top gate induces extra Dirac points in R(V_g), with the position further splitting in magnetic field. We also investigate how the magnetoresistance and quantum Hall effects of the GSL vary with the current direction with respect to the stripe domain orientation.