Evidence for unconventional electronic transport in quasicrystals

Abstract

The conductivity σ of a series of AlCuFe and AlPdMn quasicrystals and approximant phases can be written σ(T)=${\mathrm{\sigma }}_4$ K+δσ(T). The ${\mathrm{\sigma }}_{4\mathrm{}\mathrm{K}}$ term is very low, decreases with improvement of structural quality, and varies strongly with composition. δσ(T) is independent of the sample and increases anomalously with temperature up to 1000 K, with ${\mathrm{\sigma }}_{1000\mathrm{}\mathrm{K}}$/${\mathrm{\sigma }}_{4\mathrm{}\mathrm{K}}$ greater than 10. The results are interpreted by electronic hopping between structural entities separated by about 30 Å. Within a band picture, this process would correspond to interband transitions.