Quantum percolation in power-law diluted chains

We investigate the quantum percolation problem in a diluted chain with long-range hopping amplitudes. Each bond is activated with probability $p(r) = p_1/r^{\alpha}$, where $r$ is the distance between two sites and $\alpha$ characterizes the range of the interactions. The average participation ratio of all eigenstates is used as a measure of the wave-functions localization length. We found that, above a quantum percolation threshold $p_1^{(q)}$, true extended states appears for $\alpha < 1.5$. In the regime of $1.5 < \alpha <2.0$ there is no trully extended states even in the presence of a spanning cluster. Instead, a phase of critical wave-functions sets up.