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

点击翻译按钮获取中文摘要

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).