Quasicrystals, which occupy an intermediate position between crystals and amorphous materials, represent a unique platform for studying fundamental questions of solid-state physics. The absence of a periodic structure, characteristic of crystals, and the presence of long-range order, which distinguishes them from amorphous substances, determine unusual electron transport properties, in particular, magnetoresistance.
Unlike conventional metals and semiconductors, where magnetoresistance is explained by the Lorentz effect and the scattering of charge carriers on magnetic impurities, in quasicrystals the mechanisms of magnetoresistance are more complex and depend on the features of the electronic structure and the scattering of charge carriers on complex atomic configurations.
Quasicrystals exhibit an abnormally high positive magnetoresistance, which can reach tens and hundreds of percent in strong magnetic fields. This effect is associated with the existence of pseudogaps in the electron structure, caused by electron diffraction on a quasiperiodic lattice. Application of a magnetic field leads to a change in the density of states near the pseudogap and, as a consequence, to a change in conductivity.
Magnetoresistance (MR) in quasicrystals is only one of a number of anomalies manifested in their electron transport characteristics. However, this phenomenon stands out from the rest, since most of the experimental data on it can be successfully explained using the existing theoretical base. In this paper, we consider arguments in favor of the fact that quantum interference effects (QIE) allow us to adequately describe the observed phenomena in alloys with high specific resistance. This circumstance plays an important role in understanding the mechanisms of electron transport in quasicrystalline structures. Illustrations are presented of the useful information that can be extracted using QIE for analyzing transport properties.
Moreover, in some quasicrystals, oscillating magnetoresistance is observed, reminiscent of the de Haas-van Alphen effect, but having a more complex nature. These oscillations are associated with the quantization of electron orbits in the quasiperiodic potential and the formation of a fractal structure of Landau levels.
The study of magnetoresistance in quasicrystals is not only of fundamental scientific interest, but also has important practical significance for the development of new electronic devices and sensors.
Author: Ö Rapp
Institute: Solid State Physics, Royal Institute of Technology, SE 10044 Stockholm, Sweden