  Bernal-stacked multilayer graphene is a versatile platform to explore quantum
transport phenomena and interaction physics due to its exceptional tunability
via electrostatic gating. For instance, upon applying a perpendicular electric
field, its band structure exhibits several off-center Dirac points (so-called
Dirac gullies) in each valley. Here, the formation of Dirac gullies and the
interaction-induced breakdown of gully coherence is explored via
magnetotransport measurements in high-quality Bernal-stacked (ABA) trilayer
graphene. In the absence of a magnetic field, multiple Lifshitz transitions as
function of electric field and charge carrier density indicating the formation
of Dirac gullies are identified. In the quantum Hall regime and high electric
fields, the emergence of Dirac gullies is evident as an increase in Landau
level degeneracy. When tuning both electric and magnetic fields,
electron-electron interactions can be controllably enhanced until the gully
degeneracy is eventually lifted. The arising correlated ground state is
consistent with a previously predicted nematic phase that spontaneously breaks
the rotational gully symmetry.
