The hierarchical spectral flow of Bloch electron

The Hall conductance of a two-dimensional electron gas has been studied in a uniform magnetic field. The Hall conductivity is expressed as a sum of two contributions: one corresponding to the classical Drude-Zener formula, and a second which has no classical analogy. The developed theory is applied to the Hall effect. The Kobo formula is written in a form that makes apparent the quantization when the Fermi energy lies in a gap. We examine the hierarchical spectral flow of Hall conductivity.