Preface -- Contents -- Chapter 1 Theories for Photoinduced Structural Phase Transitions and their Dynamics Keiichiro Nasu -- Contents -- 1. Equilibrium Phases, Nonequilibrium Phases and Photoinduced Phase Transitions -- 2. Relaxation of Optical Excitations, Hidden Multi-Stability and Photoinduced Phase Transitions -- 3. Photoinduced Ionic Neutral Phase Transition in Organic Molecular Crystal TTF-CA -- 4. Threshold Excitation Intensity and Initial Condition Sensitivity -- 5. Adiabatic Path of Photoinduced Ionic Neutral Phase Transition in TTF-CA Crystal -- 5.1. Model Hamiltonian -- 5.2. Ground state properties -- 5.3. Energy band structure and lowest excited state -- 5.4. Relaxation path -- 5.5. High energy optical excited states in SDW state -- 6. Early Time Nonlinear Nonequilibrium Quantum Dynamics and Initial Condition Sensitivity -- 6.1. Model Hamiltonian for quantum dynamics -- 6.2. Relaxation and occurrence or nonoccurrence of the PSPT -- 6.3. Life time prolongation -- 6.4. Iterative method for exciton proliferation -- 6.5. Numerical results -- 7. Difference between Photoinduced Nonequilibrium Phase and High Temperature Equilibrium Phase -- 7.1. Photoinduced phase transition in organo-metallic complex crystal -- 7.2. Broken symmetry only in photoinduced nonequilibrium phase -- 7.3. Two-dimensional extended Peierls-Hubbard model -- 7.4. Mean field theory and phase diagram -- 7.5. Photoinduced phase -- 7.6. Hysteresis and nonadiabatic effect -- 8. Photoinduced Macroscopic Parity Violation and Ferroelectricity -- 8.1. Large polaron, self-trapped polaron, linear and quadratic couplings -- 8.2. Recent optical experiments on SrTiO3 and soft-anharmonic T1u mode -- 8.3. Possible scenario -- 8.4. Model Hamiltonian -- 8.5. Variational method for polaron -- 8.6. Continuum approximation -- 8.7. Numerical results -- 8.8. Singlet bipolaron.

8.9. Further softening and enhanced 1 -- 9. Further Problems in Photoinduced Phase Transitions -- Acknowledgements -- References -- Chapter 2 Time-Resolved Spectroscopy of the Dynamics of Photoinduced Ionic-to-Neutral Phase Transition in Tetrathiafulvalen-P-Chloranil Crystals Katsumi Tanimura -- Contents -- 1. Introduction -- 1.1. Photoinduced structural phase transitions -- 1.2. The transition between neutral and ionic phases in TTF-CA -- 1.3. Photoinduced NI transition in TTF-CA -- 2. State-sensitive and Non-linear Features of Photoinduced NI Transition -- 2.1. Threshold excitation density for metastable N-phase formation -- 2.2. The formation yield of N-phase domains vs. excitation intensity -- 3. Primary Steps in the Dynamics of Photoinduced NI Transition -- 3.1. Overview of the results of fs time-resolved spectroscopy -- 3.2. Quantitative results of three important characteristics in the dynamics -- (a) Spectral analysis of the induced changes -- (b) Excitation-intensity dependence of changes in R/R0 -- (c) Oscillatory modulation in reflection changes -- 3.3. Phenomenological analysis of the temporal evolution of NI transition -- 4. Microscopic Mechanisms of the Primary Processes in the Dynamics -- 4.1. Precursor-forming process -- 4.2. Local proliferation of neutral domains -- 4.3. N-phase order formation -- 4.4. Oscillatory modulations in reflectivity changes -- 5. CT Excited State vs. Molecular Excited State -- 6. Photoinduced vs. Temperature-induced NI Transitions -- Acknowledgments -- References -- Chapter 3 Study on the Cooperative Photoinduced Low-Spin to High-Spin State Conversion Processes Osamu Sakai and Tetsuo Ogawa -- Contents -- 1. Introduction -- 2. Formulation -- 2.1. Master equation and the ion-ion interaction -- 2.2. Transition probability -- 3. Temporal Evolution of LS Fraction based on Koshino-Ogawa's Approach.

4. Monte Carlo Simulation -- 4.1. Method of simulation -- 4.2. Results in two-dimensional case -- 4.3. Three-dimensional case -- 5. Difference and Similarity with the Temperature Induced Transition -- 5.1. The Fokker-Planck equation -- 5.2. Rate equation for the LS fraction -- 5.3. Potential barrier and nucleation of HS domain -- 6. Miscellaneous Problems -- 6.1. The Zeeman field -- 6.2. Intermittent excitation -- 6.3. Interruption of excitation -- 7. Coupling with Volume Striction Modes -- 8. Macroscopic Phase Separation -- 8.1. MC results -- 8.2. Phase coexistence condition -- 9. De-pinning of Volume Striction -- 9.1. Model of de-pinning -- 9.2. Three-dimensional case -- 10. Summary and Discussion -- 10.1. Cooperative LS to HS transition -- 10.2. Characteristics of photoinduced phase transitions (PIPTs) -- Acknowledgments -- Appendix: Phase Coexistence Condition -- References -- Chapter 4 Femtosecond Dynamics of the Photo-Induced Lattice Rearrangements in Quasi-One-Dimensional Halogen-Bridged Platinum Complexes Tohru Suemoto, Shinichi Tomimoto and Taira Matsuoka -- Contents -- 1. Introduction -- 2. Excited States in Platinum Complexes -- 3. Theoretical Background of the Relaxation Dynamics -- 4. Time-Resolved Measurements and Dynamics -- 5. Pt-Br System -- 6. Pt-Cl System -- 7. Pt-I System -- 8. Halogen Ion Dependence -- 9. Visualization of the Wave-Packet -- 10. Exciton Localization Process -- Acknowledgments -- References -- Chapter 5 Monte Carlo Simulations on Ising-Like Models for Photoinduced Phase Transitions Tohru Kawamoto and Shuji Abe -- Contents -- 1. Ising-Like Model for Photoinduced Phase Transitions -- 2. Ising-Like Model for Spin-Crossover Complexes -- 2.1. Experimental facts -- 2.2. Internal entropy effect -- 2.3. Cooperative interactions -- 2.4. Photoinduced vs. thermally induced phases -- 3. Monte Carlo Simulation Method.

3.1. Monte Carlo simulations for Ising-like models -- 3.2. Master equation -- 3.3. Transition rates -- 3.3.1. Thermal fluctuations -- (a) The Arrhenius model -- (b) The heat bath model -- (c) The Metropolis model -- 3.3.2. Quantum mechanical tunneling -- 3.3.3. Photoexcitation -- 3.4. Calculation procedure -- 4. Photoinduced Phase Transition in Uniform Systems -- 4.1. Stationary state under constant photoexcitation -- 4.2. Phase transition kinetics under photoexcitation -- 4.3. Dynamical phase transition -- 5. Photoinduced Phase Transitions in Combined Structures -- 5.1. Proposed model -- 5.2. Simulation results for superstructures -- 5.2.1. Symmetric superstructures -- 5.2.2. Generalization -- 5.3. Discussion -- References -- Chapter 6 Photoinduced Phase Transitions in One-Dimensional Correlated Electron Systems Hiroshi Okamoto, Shin-ichiro Iwai and Hiroyuki Matsuzaki -- Contents -- 1. Introduction -- 1.1. Fundamental feature of 1D correlated electron systems -- 1.2. Concepts of photoinduced phase transitions in 1D correlated electron systems -- 2. Ultrafast Photoinduced Transition from Mott Insulator to Metal in Halogen-Bridged Nickel-Chain Compound -- 2.1. Crystal and electronic structures of halogen-bridged nickel-chain compound -- 2.2. Change of electronic structure in two-dimensional cuprate by chemical carrier doping -- 2.3. Ultrafast insulator-metal transition observed in femtosecond pump-probe reflection spectroscopy -- 2.4. Relaxation dynamics of the photoinduced metallic state -- 3. Photoinduced Phase Transition in a Spin-Peierls System of Organic Radical Crystal, TTTA -- 3.1. Room-temperature optical and magnetic bistability in TTTA -- 3.2. Photoinduced phase transition in TTTA -- 4. Dynamical Aspects of Photoinduced IN and NI Transitions in TTF-CA -- 4.1. Dynamical aspect of photoinduced IN transition.

4.2. Excitation energy dependence of photoinduced IN transition -- 4.3. Coherent oscillations in photoinduced IN transition -- 4.4. Dynamical aspect of photoinduced NI transition -- 5. Phase Control and Photoinduced Phase Transition in 1D Halogen-Bridged Binuclear Platinum Compound -- 5.1. Phase control in PtPtI chains -- 5.2. Pressure-induced phase transition in PtPtI chains -- 5.3. Photo-induced phase transition in PtPtI chains -- 6. Summary -- Acknowledgments -- References -- Chapter 7 Probing Photoinduced Structural Phase Transitions by Fast or Ultra-Fast Time-Resolved X-Ray Diffraction Herve Cailleau, Eric Collet, Marylise Buron-Le Cointe, Marie-Helene Lemee-Cailleau and Shin-ya Koshihara -- Contents -- 1. Introduction -- 2. What X-Ray Scattering Can See of a Photoinduced Phase Transition Accompanied by Structural Changes? -- 2.1. Bragg diffraction from periodic lattice -- 2.2. Average structural state -- 2.3. Symmetry change -- 2.4. Dynamical physical photoinduced features -- 3. How Fast or Ultra-Fast Time-Resolved X-Ray Scattering Experiment Proceeds? -- 3.1. Fast and ultra-fast X-ray sources -- 3.2. Optical laser pump and X-ray probe techniques -- 3.3. X-ray probed volume vs. photo-excited part -- 4. First Fast or Ultra-Fast Time-Resolved X-Ray Diffraction Experiments -- 4.1. Fast probing of N-I photoinduced phase transition -- 4.2. Ultra-fast probing in hard condensed matter -- 5. Conclusion -- Acknowledgments -- References -- Index.