Janusz Sadowski and the MBE machine

New research may provide better electronic components in the future

Supported by a grant from the Swedish Research Council, researchers at Linnaeus University will conduct experimental and theoretical studies of magnetic topological materials, a field awarded the Nobel Prize in Physics 2016. Possible results of the project include new types of energy-efficient magnetoelectronic components.

Conductors, semiconductors and insulators. That is the traditional classification of materials based on their ability to conduct, partially conduct or not conduct electrical current. Examples of these three types of material are copper, silicon and plastic.

Over the past ten years, however, new materials with unique properties have been discovered, the so-called topological isolators (TI) and topological semimetals (TSM). Theoretical discoveries in the field awarded three Britons the Nobel Prize in Physics 2016, and now researchers at Linnaeus University will conduct experimental and theoretical studies of magnetic topological materials in a new project.

"The fact that electrons can not spread backwards in a material has only been observed so far in very specific cases. In topological materials, however, this can happen near room temperature and without the requirement of high material purity or an external magnetic field. The phenomenon arises at the surface or edges of TI and in the entire material of TSM," says Janusz Sadowski, Professor of Physics and Project Manager.

This unique feature implies an increased mobility of the electrons living on the surface of the material. On the other hand, the presence of nearby magnetic components can strongly modify this behavior and generate entirely novel quantum phenomena. In practice this can be achieved either by mixing layers of topological and magnetic materials, or by doping a topological material with magnetic elements such as manganese or chromium. The opposite effect can also be achieved: the topological material may be used to control the properties of ferromagnets.

"These two unique effects open up new opportunities that may lead to new magnetoelectronic components. The components also become less energy-consuming, as the higher mobility of the electrons reduces energy losses. The combination of ferromagnetic and topological materials also makes it possible to control electronic components in a completely new way," says Janusz Sadowski.

Experimental and theoretical studies

The project is entitled "Experimental and theoretical studies of magnetic topological materials and heterostructures" and starts on January 1, 2018 with a grant of SEK 3.6 million from the Swedish Research Council. The materials will be produced in a new laboratory at Linnaeus University by Molecular Beam Epitaxy (MBE), which means that atoms are applied to a substrate in thin layers under very clean conditions. The equipment for this has recently been moved from MAX-lab in Lund to Växjö. The project will also collaborate with the newly-built MAX IV synchrotron laboratory in Lund, Uppsala University, Chalmers University of Technology and, in the future, perhaps also with the upcoming European research center European Spallation Source (ESS) in Lund.

"By combining theory and experiments, the project is unique for Sweden. It builds on the theoretical studies of topological and ferromagnetic materials that have been going on for many years in the Condensed Matter Physics research group at Linnaeus University", says Carlo Canali, Professor of Physics, leader of the research group and co-appliant in the project proposal.

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