Fig. 3: Enhanced charge polarization.
From: Giant ferroelectric polarization in a bilayer graphene heterostructure
a Four states with distinct magnitudes of hysteresis. Note the satellite peaks at FFP exhibit a constant shift from CNP in all states, indicating the moiré superlattice keeps unchanged. The sweeping curves of State 2 is also denoted as the black cutting line in the inset, where the polarized charge Δn and the internal electric dipole P3D are also illustrated. b Summary of polarized charge densities in various ferroelectric systems. The 2Δn for D1 and D2 are depicted by filled circles, which are close to or well above the capability of typical moiré bands (the red dashed line: the twisted angle of 0.69° as in D1). GSFE devices from literatures are plotted as open circles33 and squares34. The horizontal grey background emphasizes that their polarization Δn actually do not depend on the thickness of gating dielectrics d. However, for others integrated in the dielectric gate, the induced charge polarization in the conduction channel is inversely proportional to the total thickness of the gating dielectrics. 1T’-WTe2, parallel-hBN and R-TMDs are taken from experiments, while monolayer α-In2Se3 from theoretical calculations.
