Investigation of the influence of chirality and frustration on magnetic properties of large molecule-based spin systems withDynamical Density Matrix Renormalization Group and relate methods

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The principal goal consists in the evaluation of spectral functions of interesting large molecule-based spin systems in the ground state (T=0) and for low-lying excited states, i.e. very low temperatures, and for applied magnetic fields. These spectral function shall be compared with experimental INS spectra. We would to understand the physical properties and to derive the parameters of the relevantHamiltonian. Technically we use (Dynamical) Density Matrix renormalization Group and Lanczos methods. We could show in previous studies that these allow to deduce Hamiltonian parameters with unprecedented accuracy.Using these methods and in collaboration with our experimental partners we would like to study several substances. One class consists in two spin tubes that are similar to rolled-up triangular lattices. Here we would like to better understand their behaviour in a magnetic field and investigate the influence of a possible Dzyaloshinskii-Moriya interaction. Another class is given by the Keplerate molecules {Mo72V30} and {W72V30} which are similar to the Kagome lattice. Thanks to the small vanadium spin of s=1/2 they can be treated quasi exactly. Both classes are highly frustrated spin systems with unusual excitation spectra. For Keplerates we plan to extend our investigations to larger spins.Another focus will be given by helical systems, that are interesting and for which INS is well-suited. We expect chiral magnetic states stabilized by anisotropy. To summarize our goals in one sentence: we want to investigate the influence of chirality and frustration on magnetic properties of large molecule-based spin systems. Of course we plan to incorporate new compounds of our partnersinto our investigations.