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 qua ntum Hall effect (IQHE) system is studied based on a lattice mode], wh ere the IQHE states exist only within a finite range of Fermi energy i n the presence of disorders. A two-parameter scaling law is found at t he high-energy boundary where direct transitions from high filling-fac tor IQHE states to an insulator occur. We find that rho(xx) = rho(xy) at the critical point whose value can continuously vary as a single fu nction of the Landau-level filling number n(v). Such a new universalit y well explains the recent experiment by Song et al.