Evidence for unconventional electronic transport in quasicrystals

Abstract

The conductivity \ensuremath{\sigma} of a series of AlCuFe and AlPdMn quasicrystals and approximant phases can be written \ensuremath{\sigma}(T)=${\mathrm{\ensuremath{\sigma}}}_{4}$ K+\ensuremath{\delta}\ensuremath{\sigma}(T). The ${\mathrm{\ensuremath{\sigma}}}_{4\mathrm{}\mathrm{K}}$ term is very low, decreases with improvement of structural quality, and varies strongly with composition. \ensuremath{\delta}\ensuremath{\sigma}(T) is independent of the sample and increases anomalously with temperature up to 1000 K, with ${\mathrm{\ensuremath{\sigma}}}_{1000\mathrm{}\mathrm{K}}$/${\mathrm{\ensuremath{\sigma}}}_{4\mathrm{}\mathrm{K}}$ greater than 10. The results are interpreted by electronic hopping between structural entities separated by about 30 \AA{}. Within a band picture, this process would correspond to interband transitions.