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

主要目标包括评估基态（T=0）、低洼激发态（即极低温度）和外加磁场下有趣的大分子自旋系统的光谱函数。这些谱函数应与实验INS谱进行比较。我们要了解它的物理性质，并推导出相关的密尔顿量的参数。技术上我们使用（动态）密度矩阵重整化群和Lanczos方法。我们可以在之前的研究中证明，这些可以以前所未有的精度推断哈密顿参数。使用这些方法并与我们的实验伙伴合作，我们想研究几种物质。一类由两个类似于卷起的三角形晶格的自旋管组成。在这里，我们想更好地了解它们在磁场中的行为，并研究可能的Dzyaloshinskii-Moriya相互作用的影响。另一类是类似于Kagome晶格的Keplerate分子{Mo72V30}和{W72V30}。由于钒的自旋很小（s=1/2），所以它们可以被准精确地处理。这两类都是具有异常激发光谱的高度受挫自旋系统。对于开普勒，我们计划将我们的研究扩展到更大的旋转。另一个重点将是螺旋系统，这很有趣，而且非常适合INS。我们期望手性磁态被各向异性所稳定。用一句话概括我们的目标：我们想要研究手性和挫折对大分子基自旋体系磁性能的影响。当然，我们计划将合作伙伴的新化合物纳入我们的研究中。

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.