New Quantum Materials
Some materials are not easily described with conventional, textbook, condensed matter physics laws. These quantum materials can exhibit exotic properties that could help improve information technology (for example: being able to build quantum computers). Additionally, they can be hosts of completely new physics and can even help to increase our understanding of the universe. New exciting phenomena are rapidly predicted by theoretical physicists. In order to study these properties, materials that fulfill the requirements need to be discovered first. This is where chemistry comes into play. Combining lessons from inorganic chemistry with electronic structure calculations gives predictive power to find these materials. After identifying interesting candidates, we will synthesize and characterize them.
Our group operates with the following procedure: First, inspiration comes from recognizing patterns in electronic structure, crystal structure, and properties of known materials. Then, this knowledge is used to find a compound that could be a starting point to realize a desired property in a new material. Chemical concepts about bonding and electron count are the most important tools for achieving this. Subsequently, the electronic structure is calculated using available codes. If it confirms the initial idea, the material will be synthesized and characterized. To make the new materials, we use the combined knowledge of solid state chemistry, including methods such as flux growth, vapor transport, and Bridgman growth. Finally, if the crystal structure assumed for the electronic structure calculation and the real crystal structure match, the properties can be measured.
Some materials have to be described mathematically completely differently from others because they have a different topology. In such topological materials, electrons can behave differently (for example, they can behave like photons). Additionally, it is possible that particles that are only known from high energy physics that require very expensive experiments to be discovered and studied, can be realized as quasiparticles in these materials. In our group, we predict new topological materials and grow single crystals of them, which we then study in our lab and in collaboration with the physics department
Magnets in two dimensions
Nearly all known magnetic materials are three dimensional materials. Some compounds are layered and exhibit magnetic order, but are technically still 3D materials. If those are exfoliated, magnetic 2D nanosheets can be made. Thus far, scientists have primarily exfoliated magnetic materials with very high air sensitivity with adhesive tape. In our group, we apply a different method: chemical exfoliation. In chemical exfoliation, suspensions of magnetic nanosheets can be made. The sheets can then be transferred to any substrate and studied. In this way, we can make much larger and uniform 2D materials. Such 2D magnets are of interest for data storage applications or for fabricating devices where a very thin magnetic layer is needed. They can also be used to create devices where a magnetic layer needs to be brought into close contact with a different material.