The localized eigenstates of the Harper equation exhibit universal self-similar fluctuations once the exponentially decaying part of the wave function is factorized out. For a fixed quantum state, we show that the whole localized phase is characterized by a single strong coupling fixed point of the renormalization equations. This fixed point also describes the generalized Harper model with next nearest neighbor interaction below a certain threshold. Above the threshold, the fluctuations in the generalized Harper model are described by a strange invariant set of the renormalization equations.

• Received 25 April 1995

DOI:https://doi.org/10.1103/PhysRevLett.75.2762