International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

Iron-based unconventional superconductors have attracted intense interest after the critical temperature of FeSe was enhanced by more than one order of magnitude. This was achieved for FeSe placed on top of an insulating oxide substrate with its thickness reduced to the nanometer limit. There are numerous indications of the critical importance of specific features of the FeSe electronic structure in the vicinity of the Fermi surface. Here, we explore how the FeSe band topology changes when located on a Si(001) surface, by first-principles calculations based on the density functional theory. We determine which interface arrangement is preferred and what is the optimal distance between FeSe and Si. Our calculations reveal interesting effects of Si proximity on the FeSe band structure. Bands corresponding to hole pockets at the Γ point in NM FeSe are generally pushed down below the Fermi level. We explain these changes by a redistribution of electrons between different Fe orbitals rather than charge transfer to/from Si.

Magnetic van der Waals (vdW) materials composed of two-dimensional (2D) layers bonded to one another through weak interactions exhibit promising potentials for high-tech magnetic, magneto-electric, and magneto-optic applications in nanostructures. Due to their intrinsic magnetocrystalline anisotropy, several vdW magnets could be thinned down to nanoscale thickness, while still maintaining magnetism. Prominent examples of such materials are transition metal trihalides, in particular CrI3, a first atomically thin ferromagnet, realized in 2017.
Recently, VI3 has been found to belong among 2D ferromagnets at temperatures below 50K. It is a semiconductor undergoing a subtle structural phase transition at 78K. Furthermore, its magnetic anisotropy exhibits rather unusual features. We have studied its properties by first principles calculations and reproduced the unusual magnetic anisotropy. Its properties have been linked to lattice distortions present at some of its low temperature phases.