Mobility Gap and Anomalous Dispersion

Abstract

It is shown that anomalous dispersion of quasiparticles leads to nonpropagating states. Therefore regions of anomalous dispersion define a sort of "mobility gap." Using the coherent-potential approximation, we calculate the conditions for obtaining such a mobility gap in a disordered binary alloy. Just outside the mobility edges located at ${\omega }_c$ the mobility vanishes as $|\omega -{\omega }_c|$.