New universality of metal-insulator transition in integer quantum Hall effect system

A new universality of metal-insulator transition in integer quantum Hall effect (IQHE) system is studied based on a lattice model, where the IQHE states only exist within a finite range of Fermi energy in the presence of disorders. A two-parameter scaling law is found at the high-energy boundary where direct transitions from high IQHE states to insulator occur. We find $\rho_{xx}= \rho_{xy}$ at the critical point whose value can continuously vary as a single function of the Landau-level filling number $n_{\nu}$. Such a new universality well explains recent experiment by Song et al. (Phys. Rev. Lett. 78, 2200 (1997)).