Stacking-Induced Ferroelectricity in Tetralayer Graphene

Pristine mono- or few-layer graphene lacks a permanent dipole due to its centrosymmetric lattice, making ferroelectricity unlikely. However, ABCB tetralayer, the simplest mixed-stacked graphene, breaks both inversion and mirror symmetry, thus exhibiting intrinsic out-of-plane polarization arising from asymmetric charge carrier distribution across its layers. We report robust ferroelectric behavior in ABCB tetralayer graphene encapsulated in hexagonal boron nitride, in the moiré-less limit. The device exhibits pronounced hysteresis in resistance under both top and bottom gate modulation, with the effect persisting up to room temperature. This hysteresis originates from reversible layer-polarized charge reordering, driven by gate-induced transitions between ABCB and BCBA stacking configurations. Our findings establish stacking-order-induced symmetry breaking as a fundamental route to ferroelectricity and open pathways for nonvolatile memory applications.