Search for kagome Weyl type III semimetals.

• Applicants: Professor Dr. Bernd Büchner; Dr. Sabine Wurmehl
• Subject Area: Experimental Condensed Matter Physics
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 545855024

Topologically non-trivial semimetals are currently at the forefront of research in condensed matter physics, not only because of their unusual properties, but also because of their potential applications in a new generation of electronics for quantum computing and spintronics. Dirac semimetals and Weyl semimetals are three-dimensional phases of matter with gapless electronic excitations that are protected by both topology and symmetry. Dirac and Weyl semimetals have a typical conical dispersion and a point-like Fermi surface and their electron band dispersion does not have to obey Lorentz invariance. As a result, their dispersion cones can be tilted, giving rise to new band dispersions called Weyl/Dirac points of types II and III and, respectively, Weyl/Dirac semimetals of types II and III. To date, no material has been experimentally verified as a Weyl III semimetal. The objective of our project is to address this gap by striving to unveil and validate the first Weyl III semimetal by an international team from Dresden and Kiev. The PLs combine well-renowned expertise in crystal growth, characterization of magnetic and thermodynamic properties and electronic structure exploration by both ARPES and electronic transport measurements supported by theory, hence, by building an interdisciplinary project team. We focus on the exploration of less or not at all explored Co-based shandites as candidates for being kagome semimetals. Specifically, we will systematically investigate magnetic Co3M2(S,Se)2 shandites with M= Sn,In,Pb,Ge which are predicted to be Weyl III semimetal. We will utilize doping and chemical pressure to control and modify their respective electronic structure. By combining the results obtained with complementary methods, we will gain a better understanding of the influence of non-trivial topology on the properties of Shandite-based Weyl semimetals.

• DFG Programme: Research Grants
• International Connection: Ukraine
• International Co-Applicant: Professor Dr. Alexander Kordyuk