Single crystal growth of tunable coupled-dimer systems and triangular antiferromagnets

Dr. Franz Ritter
Physikalisches Institut, J.W. Goethe-Universität Frankfurt
Tel.: +49-69-798-47259
Fax: +49-69-798-47270
E-mail: F.Ritter(at)

Prof. Dr. Wolf Aßmus
Physikalisches Institut, J.W. Goethe-Universität Frankfurt
Tel.: +49-69-798-47258
Fax: +49-69-798-47270
E-mail: assmus(at)

Prof. Dr. Cornelius Krellner
Physikalisches Institut, J.W. Goethe-Universität Frankfurt
Tel.: +49-69-798-47295
Fax: +49-69-798-763-47295
E-mail: krellner(at)

The aim of this project is the single crystal growth and characterization of Cu-based quantum spin systems, which serve as model systems to study quantum many-body effects. One important aspect is the role of magnetic frustration, which is closely connected to the geometric arrangement of the Cu2+ spins in the different structure types. The main focus is on the two-dimensional (2D) triangular-lattice spin-1/2 Heisenberg antiferromagnets, Cs2CuCl4-xBrx. A second material class, studied within that project, is the alkaline earth Cu cyclosilicate, BaCuSi2O6, a good experimental realization of a spin-1/2 dimer system. Recently, we started to work on another material class with pronounced frustration, the 2D kagome system, ZnxCu4-x(OH)6Cl2.

Close collaboration is carried out with the following projects within the SFB/TR 49: B1 (Wolf/Lang) investigates low-temperature magnetic and thermodynamic properties near the field-induced quantum-critical points to study the interplay between geometrical frustration and spin-lattice interactions. DFT calculations on all material classes are performed in B2 (Jeschke/Valentí) with concrete predictions for electron-doped Herbertsmithite. Quantum Monte-Carlo (QMC) simulations of thermodynamic observables are done in B3 (Eggert) on coupled spin-dimer systems.

In 2012, Prof. Dr. Wolf Aßmus was retired but he is still actively involved in this research project as a senior professor. With the appointment of Prof. Dr. Cornelius Krellner as successor of Prof. Dr. Wolf Aßmus, an expert in materials science with a strong background in the field of strongly correlated electron systems joined the SFB/TR49. His research focus is on quantum critical materials which is also at the heart of the research activities within this project. Therefore, a successful continuation of this project is ensured.