  We explore the non-equilibrium transport regime in graphene using a large dc
current in combination with a perpendicular magnetic field. The strong in-plane
Hall field that is generated in the bulk of the graphene channel results in
Landau levels that are tilted spatially. The energy of cyclotron orbits in the
bulk varies as a function of the spatial position of the guiding center,
enabling us to observe a series of compelling features. While Shubnikov-de Haas
oscillations are predictably suppressed in the presence of the Hall field, a
set of fresh magnetoresistance oscillations emerge near the charge neutrality
point as a function of dc current. Two branches of oscillations with linear
dispersions are evident as we vary carrier density and dc current, the velocity
of which closely resembles the TA and LA phonon modes, suggestive of
phonon-assisted intra-Landau level transitions between adjacent cyclotron
orbits. Our results offer unique possibilities to explore non-equilibrium
phenomena in two-dimensional materials and van der Waals heterostructures.
