Imaging tunable quantum Hall broken-symmetry orders in charge-neutral graphene

Charge-neutral graphene under perpendicular magnetic field was predicted to harbor a rich variety of many-body ground states with distinct topological and symmetry breaking orders. In this talk, I present atomic-scale imaging of the electronic wavefunction of three distinct broken-symmetry phases in graphene using scanning tunneling spectroscopy. We explored the phase diagram by controllably tuning the magnetic field and the screening of the Coulomb interaction by close proximity to a low or high dielectric constant substrate. In the unscreened case, we unveiled a Kekul´e bond order. Under dielectric screening, a sublattice-unpolarized ground state emerged at low magnetic fields, and transited to a charge-density-wave order with partial sublattice polarization at higher magnetic fields. This screening-induced tunability of broken-symmetry orders may prove valuable to uncover correlated phases of matter in other quantum materials.