Relaxation of metastable state through the quantum dynamics

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We have studied the following phenomena in which the, quantum dynamics plays an important role. We investigated the quantum hysteresis phenomena in nanoscale molecular magnets such as Mn12, Fe8 and V15 in the view point of non adiabatic transition. We studied the effects of the environments, such as the phonon, the dipole interaction and hyperfine interactions with the nuclear spins, on the quantum dynamics. In particular, we clarified mechanisms of deceptive non-adiabatic transition at very low temperature, of the parity effect due to the thermally excited states and of the quantum foehn phenomena due to inflow of the heat. We also developed a new direct numerical method to study the line shape of ESR in strongly interacting quantum spin systems, and investigate the dynamical shift due to the dipole interaction, anisotropy and DM interactions. The slow dynamics due to the inhomogeneity in the systems such as spin glass and random bond system. In quantum systems, the local magnetization is often induced at inhomogeneous parts of lattice in the so-called gapped quantum spin systems which is non-magnetic in the ground state. We studied how the local magnetizations are induced in various systems and also investigate the dynamical properties. We also investigated the quantum spin dynamics for quantum computing, and found a kind of instability in the spin manipulation.