New Universality of the Metal-Insulator Transition in an Integer Quantum Hall Effect System

A new universality of the metal-insulator transition in an integer quantum Hall effect (IQHE) system is studied, based on a lattice model, where the IQHE states exist only 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 filling-factor IQHE states to an insulator occur. We find that ${\rho }_{\mathrm{xx}}={\rho }_{\mathrm{xy}}$ 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 the recent experiment by Song et al. [Phys. Rev. Lett. 78, 2200 (1997)].