The difference is in the length and energy scales. Lattice constants of atomic crystals are of the order of 1Å while those of superlattices (a) are several hundreds or thousands larger as dictated by technological limits (e.g. electron-beam lithography used for the patterning of the heterostructure surface). Energies are correspondingly smaller in superlattices. Using the simple quantum-mechanically confined-particle model suggests E ∝ ∝ 1 / a 2 . This relation is only a rough guide and actual calculations with currently topical graphene (a natural atomic crystal) and artificial graphene (superlattice) show that characteristic band widths are of the order of 1 eV and 10 meV, respectively. In the regime of weak modulation ( | V 0 | ≪ ≪ E f ), phenomena like commensurability oscillations or fractal energy spectra (Hofstadter butterfly) occur.