Graphene-based (and similar) nanostructures for spintronics and spin caloritronics. Theoretical studies
Project results
Studies carried out within the present project are devoted to the search for new materials for modern electronics. In view of the quickly progressing miniaturization process, these materials have to be scalable, i.e. they must maintain their physical properties even if they are extremely small (of the order of 1nm=10-9m) when the principles of quantum mechanics come into play. It is important to make use of not only the charge but also the spin of electrons, so as to enhance technological capabilities. Then spintronics (magneto-electronics) or spin caloritronics (in the case of heat transport) are dealt with.
The ‘Harmonia’ project research was carried out by Institute of Molecular Physics (IMP) and A. Mickiewicz University (UAM) in Poznan, and Technical University in Dresden (TUD). Prof. Dr. G. Cuniberti, a world-class expert in molecular physics and nanotechnology, was the Leading Foreign Partner. The present studies have been focused on graphene and graphene-like structures. While graphene is a flat single-layer structure of carbon atoms arranged in a honeycomb fashion, other similar structures are in general quasi 2-dimensional with some out-of-plane buckling. It has been shown that these materials have quite interesting physical properties for potential applications in spintronics and spin caloritronics. The results show that electronic edge states play a crucial role both in narrow ribbon-shaped nanostructures and in nanoflakes. These states may lead to the appearance of the magnetization at the edges, and thereby to significant changes in both electrical and thermal conductances. Another valuable finding is the identification of main underlying physical mechanisms which are responsible for the observed properties. The following factors have been taken into account: intraatomic Coulomb repulsion, spin-orbit coupling, the presence of magnetic and electric fields and proximity effects coming from a substrate. The following structural imperfections have been also taken into account: the aforementioned edge effects, inter-grain boundaries in polycrystalline carbon nanostructures, and the so called antidots (empty regions). Successful explanation of these problems makes the project innovative from the scientific point of view. It may also have some practical significance, as concerns perspective developments of spintronics and spin caloritronics owing to the following findings: (i) significant giant magnetoresistance and possibility to generate spin-polarized currents, and (ii) great value of the so-called figure of merit (ZT), what e.g. in the case of silicene (2-D silicon) gives hope for the construction of new nanoscale thermoelectric devices.
The project achievements can contribute to faster development of new energy saving technologies and thereby – to the environmental protection and the economic growth.