Anderson localization of electron states in a quasicrystal

Abstract

The influence of disorder on the critical electron states in a quasiperiodic lattice is a subject of intense research. In this work, we report the occurrence of Anderson localization in an icosahedral (i) polygrain quasicrystal Al-Pd-Re due to site disorder using hard x-ray photoemission spectroscopy, resistivity, and density functional theory (DFT). Photoemission spectroscopy shows that the density of states is enhanced at the Fermi level in polygrain $i$-Al-Pd-Re compared to single-grain $i$-Al-Pd-Re. In contrast, the conductivity of the former is an order of magnitude reduced compared to the latter, indicating that these electron states are localized. DFT shows that these states originate primarily from Re $5d$-Pd $4d$ hybridization and are enhanced in polygrain $i$-Al-Pd-Re due to compositional difference, but are broadened because of disorder that brings about Anderson localization. This is established by the Mott variable range hopping behavior of conductivity, and the estimated localization length is 23 \AA{}.