Localization in a Magnetic Field: Tight Binding Model W I T H One-half of a Flux Quantum per P L a Q U E I T E

The conduction properties of a two-dimensional tight-binding model with on-site disorder and an applied perpendicular magnetic field with precisely one-half of a magnetic flux quan tum per plaquette are studied. A cont inuum hamiltonian is derived which enables the construction of a field theory for the diffusive modes. The field theory is shown to be in the universality class of the O(2n,2n) /O(2n) × O(2n)(n--* 0) non-linear o-model implying that all the electronic states are localized. The system is shown to be related, via an analytic continuation, to a system of self-interacting fermions in 1 + 1 dimensions, in the n --* 0 limit.