  The topology of the band structure, which is determined by the lattice
symmetries, has a strong influence on the transport properties. Here we
consider an anisotropic honeycomb lattice and study the effect of a
continuously deformed band structure on the optical conductivity and on
diffusion due to quantum fluctuations. In contrast to the behavior at an
isotropic node we find super- and subdiffusion for the anisotropic node. The
spectral saddle points create van Hove singularities in the optical
conductivity, which could be used to characterize the spectral properties
experimentally.
