Electronic wavefunctions and flux quantization in the pseudomagnetic quantum limit

Deliberate triaxial strain of a monolayer graphene flake realizes an uniform static axial magnetic gauge field for the embedded massless Dirac fermions. Such a field leads to the formation of a set of pseudo Landau levels, and in particular to a topologically protected Landau level located precisely at zero energy. Thanks to its extraordinary tunability, molecular graphene offers an unprecedented platform that can access fields at the moderate to ultra quantum limit where the magnetic length scale is comparable to the lattice constant. We experimentally demonstrate that such a pseudomagnetic field supports the zeroth Landau level at the band center up to 300 T when the Landau level wavefunctions are confined within a few unit cells. Nonetheless, via detailed mapping of the corresponding electronic wave functions, we show that the axial magnetic field displays flux quantization within the cyclotron orbit, even when its dimension is comparable to the lattice constant.