New topological 4f quantum magnets beyond textbook

4f quantum magnets are increasingly becoming the focus of current research because new exotic magnetic ground states can be found due to the spin-orbit interaction and the different configurations of the 4f ions. In particular, Kramers ions, which can be regarded as spin 1/2 ions, exhibit spin liquid-like ground states [1,2]. In reduced, excellent geometries such as honeycombs (f.i. BiYbGeO₅ [3] or YbCl₃ [4] ), triangles [1,5], or Kagome lattices [6], spin liquid ground states with and without a gap in the magnetic excitation spectrum can be found.

In novel Yb compounds with a more three-dimensional structure, such as YbAlO₃ and Yb₂Pt₂Pb, new magnetic excitations known as spinons have been discovered. Spinon excitations interact with phononic excitations, resulting in unusual ground state properties. [7,8].

Leaving aside the route of quasi spin 1/2 Kramer ions, there is a wide field of as yet unexplored compounds with completely new magnetic properties. Prominent examples are Tm triangular lattices such as the quantum Ising magnetism in KTmSe₂ [9] or the ferroquadrupolar transition in TmVO₄ [10].

In this project, the potential applications for a PhD student are wide-ranging. The portfolio covers material synthesis and bulk characterization (magnetization, specific heat) as well as solid-state spectroscopy (NMR and ESR) and neutron spectroscopy. In addition, theoretical calculations on exchange models and band structure will be implemented.