Optical spectroscopy study of the interplay between Dirac electrons, magnetism, and charge density waves in square-net materials

• Applicant: Professorin Dr. Christine Kuntscher
• Subject Area: Experimental Condensed Matter Physics
• Term: since 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 411090417

Square-net materials with topological electronic band structure such as the prototypical nodal-line semimetal ZrSiS are currently intensively investigated. Topological Dirac semimetals possess linearly dispersing electronic bands, which cross at certain points in reciprocal space, and show exceptional physical properties. In nodal-line semimetals the crossing points lie on a line or closed loop, and they can be viewed as 3D analogues of graphene hosting 2D Dirac electrons. Within this project, the ZrSiS-related square-net materials LnSbTe will be studied, where the Ln sites are occupied by lanthanide atoms inducing intrinsic magnetism. Therefore, LnSbTe compounds host a magnetic topological nodal-line semimetallic state at low temperatures. It was furthermore demonstrated that suitable substitution and vacancy concentration cause structural distortion and the development of charge density waves (CDWs) in LnSbxTe2−x-delta compounds, which enables an electronic band engineering and can generate novel topological phases. We will characterize the interplay between Dirac electrons, magnetism, and CDWs in the compounds LnSbxTe2−x-delta in terms of the charge dynamics by temperature-dependent optical spectroscopy. Furthermore, we will explore how external pressure tunes this interplay by optical spectroscopy measurements under hydrostatic pressure, since pressure is expected to strongly affect the CDW-related lattice distortion and hence also the electronic band structure.

• DFG Programme: Research Grants