Mechanism of magnetization induction and its dynamics in strongly correlated quantum spin systems

我们研究了量子自旋系统中量子力学效应所固有的新特性，并研究了它们的机理。特别地，我们主要研究了一维海森堡模型的性质。其中一个主题是空间不均匀性的影响。我们澄清了温度依赖的磁化曲线在晶格的边缘，也在交替键海森堡模型的交替缺陷的不稳定性诱导的磁化。这些磁化强度可以看作是一个孤立的磁化强度，我们还研究了在扫描场中磁化强度的量子动力学。我们还研究了强关联自旋系统的电子自旋共振（ESR）。我们发现反铁磁团簇中存在所谓的反铁磁共振和顺磁共振。还研究了梯形系统中共振位置的变化与温度的关系。通过量子Monte Carlo模拟研究了自旋-Peierls跃迁的有序化过程，揭示了键交替随温度的变化规律。我们发现，在高温下，大量的波动，导致偏离邦纳-费舍尔曲线的磁化率。我们将研究扩展到S=1的情况，其中自旋Peierls跃迁发生在Halfenz态和键交替态之间。研究了噪声对纳米分子磁体量子力学动力学的影响，提出了噪声诱导的平方根时间行为和绝热过程中少量热流入导致的磁化平台机制（磁性Feohn效应）。

We have studied novel characteristics inherent to quantum mechanical effects in quantum spin systems, and investigated their mechanics. In particular, we mainly studied the properties of one dimensional Heisenberg models. One of the topics is the effect of spatial inhomogeneity. We clarified the temperature dependence of the magnetization profile at the edges of the lattice and also the inhomogeneity-induced magnetization at defect of the alternation in bond-alternate Heisenberg models. These magnetization can be regarded asan isolated magnetization, and we also studied the quantum dynamics of the magnetization in the sweeping field. We also studied the electron spin resonance (ESR) in strongly correlated spin systems. We found that the coexistence of so-called antiferromagnetic resonance and the paramagnetic resonance in antiferromagnetic cluster. Temperature dependence of the shift of the resonant position was also studied on the ladder system. The ordering process of spin-Peierls transition was also studied by quantum Monte Carlo simulation where we show how the bond-alternation develops as the temperature decreases. We found large amount of the fluctuation at high temperatures which cause the deviation of the susceptibility from the Bonner-Fisher's curve. We extend the study to the case of S=1 where the spin-Peierls transition takes place between the Haldane state and the bond-alternating state. We found the transition is of the first order and obtained the shape of the domain wall between the two nonmagnetic states.The noise effects on the quantum mechanical dynamics of nanoscale molecular magnets were extensively studied and we proposed the noise induced square-root time behavior and also a mechanism of magnetization plateau due to small inflow of the heat in the adiabatic process (magnetic Feohn effect).