| We study dynamical properties of one-dimensional correlated electrons coupled with enviroment. There are two topics in this study: one is whether the spin-charge separation is robust in materials where electrons strongly interact with phonons. Since the separation provides novel optical properties such as gigantic third-order nonlinear response, it should be understood how the separation is realized in materials. Starting with the Hubbard-Holstein model at half-filling, we calculate the single-particle excitation spectrum by using the dynamical density matrix renormalization group (DMRG) method. We find that the spin-charge separation is robust in the presence of the electron-phonon coupling. However, both of the spinon and holon branches are affected by phonons. For interpretation of the DMRG results, we propose an effective model for the spectrum that is defined by a superposition of spectra for ther Holstein model. The second topic is time evolution of correlated electrons coupled with localized spins. One motivation is ultra-fast photoinduced phase transition recently observed in cuprates, manganites, and organic compounds. Here, the energy dissipation plays a crucial role. Since the exchange energy is large in some oxides, the fast relaxation may be possible by emitting magnon excitations. Starting with the extended double-exchange model, we study the transient spectrum of mobile electrons and time evolution of the spin-spin correlation for localized spins by using the time-dependent DMRG method. We discuss the effect of the spin degrees of freedom on the relaxation. |
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