Supersymmetry and localization in the quantum Hall effect

We study the localization transition in the integer quantum Hall effect as described by the network model of quantum percolation. Starting from a path integral representation of transport Green functions for the network model, which employs both complex (bosonic) and Grassmann (fermionic) fields, we map the problem of localization to the problem of diagonalizing a one-dimensional non-hermitian Hamiltonian of interacting bosons and fermions. An exact solution is obtained in a restricted subspace of the Hilbert space which preserves boson-fermion supersymmetry. The physically relevant regime is investigated using the density matrix renormalization group (DMRG) method, and critical behavior is found at the plateau transition. (C) 1997 Elsevier Science B.V.