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【摘要】

Electron crystalizes when Coulomb interaction is largely greater than kinetic energy. In two dimensions, the kinetic energy of the electrons can be further quenched by applying a perpendicular magnetic field. The so-called magnetic field induced Wigner Crystal (WC) forms at low Landau level filling factor \nu and has been extensively studied during the past 40 years. However, direct visualization of its lattice structure and symmetry has never been confirmed. Here, we perform high resolution scanning tunneling microscopy (STM) at mK temperature in Bernal-stacked bilayer graphene. We reveal the crystal symmetry of the WC and identify the relationship between the lattice constant and the filling factor \nu of the crystal.. Our study provides unambiguous evidence of the WC and paves the way for imaging exotic phases such as, skyrme crystal, quasi-particle WC, stripe phases, and bubble phases, etc..