Dirac materials in square lattice compounds

• Applicant: Dr. Christian Reinhard Ast, since 9/2017
• Subject Area: Experimental Condensed Matter Physics ; Solid State and Surface Chemistry, Material Synthesis ; Physical Chemistry of Solids and Surfaces, Material Characterisation
• Term: from 2017 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 335449904

Materials that exhibit the same electronic structure as graphene but are three dimensional (so called 3D Dirac Semimetals) have received a lot of attention recently from both fundamental and applied sciences. For once they exhibit exceptional physical properties such as very high magnetoresistance or carrier mobility, but they can also lead to the discovery of new particles that were predicted in high energy physics, but can be observed in the solid state if the materials has the correct band structure. Currently the amount of such 3D Dirac semimetals is limited and many of them show either drawbacks in their fundamental properties, i.e. their electronic structure or also in their potential to be used in future devices due to their toxicity, cost or instability in ambient conditions. The aim of this proposal is to find more 3D Dirac materials that do not bear these disadvantages. Recently we introduced a new material, ZrSiS, that is not only a cheap stable and non toxic alternative to current 3D Dirac materials, but also has an electronic structure that is of interest for fundamental physics. On the one hand the Dirac bands are linearly dispersed over a very large range of energy which allows for more defects in the crystals while still having the Fermi level located within the region of linearly dispersed bands. On the other hand ZrSiS features a Dirac cone that is protected by non-symmorphic symmetry, a transnational symmetry element that has gained significant interest by theorists for the prediction of new Dirac materials and also new fermions. We showed for the first time that it is possible to observe this predicted feature in the electronic structure experimentally. Now, we would like to expand the number of materials with related electronic structures. ZrSiS is a good starting point to look for more materials with this interesting physical properties. For once, it crystallizes in a common crystal structure (PbFCl structure type), but also, the important feature for the electronic structure can be traced back to the square net arrangement of atoms, a feature that can also arise in many more structure types, allowing for a very large number of compounds to explore. We will identify materials of interest with ab initio calculations, synthesize them, and investigate them with angle resolved photoemission spectroscopy (ARPES) and transport studies.

• DFG Programme: Research Grants
• Ehemalige Antragstellerin: Professorin Dr. Leslie Mareike Schoop, until 8/2017