Interplay between charge ordering and isospin polarization in hBN-aligned twisted monolayer-bilayer graphene

Twisted graphene hosts various strongly correlated phases governed by the interplay between charge, spin, and valley degrees of freedom. Correlated insulating states at fractional moiré fillings are often associated with charge ordering like charge density wave (CDW), which may break the moiré translation symmetry. Identifying the isospin ground states of charge ordered phases is essential for elucidating their microscopic origin, yet remains experimentally challenging. Here we report signatures of intertwined charge ordering and isospin polarization in twisted monolayer–bilayer graphene (tMBG), where the monolayer graphene is aligned with the hexagonal boron nitride (hBN) dielectric. By tuning the displacement field, a rich set of correlated states at fractional moiré fillings is observed at ν = +1/4, +1/2, +5/4, +3/2, +5/2, +7/2, -13/4, -7/2, and -15/4, in addition to integer filling states. On the electron-doped side, the CDW state at ν = +1/4 seems to be valley-polarized, whereas ν = +1/2 and +3/2 states behave consistent with spin polarization. On the hole-doped side, the ν = -7/2 and -15/4 states exhibit a temperature-enhanced insulating response reminiscent of the isospin Pomeranchuk-like effect. These results establish hBN-aligned tMBG as a highly tunable moiré platform for exploring electron crystallization and isospin order in flat minibands, offering a general route to the physics underlying interaction-driven symmetry breaking.