Occupying an intermediate position between crystalline and amorphous materials, quasicrystals represent a unique platform for investigating fundamental questions in condensed matter physics. The lack of translational symmetry inherent in quasicrystals gives rise to exotic electronic properties, including fractal energy spectra and charge carrier localization.
This study is devoted to the study of the evolution of quantum interference effects in thin films of quasicrystalline Al-Cu-Fe alloy with a change in film thickness. The use of the molecular beam epitaxy method allowed us to obtain high-quality films with controlled thickness in the range from several monolayers to tens of nanometers.
This paper presents the results of a study of the electrical conductivity characteristics of thin i-Al-Cu-Fe layers. We have recorded clear signs of changes in the nature of conductivity depending on temperature and magnetic field for samples with a thickness of less than≃103 Å, indicating a dimensional transition. In particular, for the thinnest sample, the magnetoconductivity exhibits pronounced anisotropy, which is consistent with theoretical predictions for weak localization in two-dimensional space.
These experimental results clearly demonstrate the effects of quantum interference caused by the presence of disordered structure, characteristic of quasicrystals. The obtained estimates of the microscopic parameters of electron transport are consistent with similar values established for massive samples. An analysis of the significance and interpretation of the obtained parameter values is carried out.
Experimental studies, including scanning tunneling microscopy and spectroscopy, demonstrated significant changes in the local electron density of states (LDOS) depending on the film thickness. In thin films, pronounced interference patterns were observed, associated with the scattering of electron waves by a quasi-periodic potential. With increasing film thickness, the interference effects became less pronounced, which is apparently due to an increase in the role of inelastic scattering and three-dimensional effects.
The obtained results allow us to trace the transition from two-dimensional quantum interference effects in thin films to three-dimensional behavior in thicker films. These data are important for understanding the electronic properties of quasicrystals and developing new materials based on them.
Author: T. Grenet & F. Giroux
Institute: LEPES-CNRS, 25 avenue des Martyrs, PO Box 166, 38042 Grenoble, France, Grenoble, France