Zero modes for Dirac fermions on a sphere with fractional vortex

Normalized zero-energy states are shown to emerge for massless Dirac fermio ns in an external gauge field that gives rise to nonquantized vortices on a sphere. A field-theory model is used to describe electronic states of a fu llerene-like molecule. In particular, we predict the existence of exactly o ne zero-energy mode due to a disclination. For 60 degrees disclination, the normalized electron density at zero energy is found to behave as R-5/3, wi th R being the fullerene radius. (C) 2000 MAIK "Nauka/Interperiodica".