Jun Ohara

Optical characterization of platinum-halide ladder compounds

New varieties of quasi-one-dimensional halogen (X)-bridged transition-metal (M) complexes, (C_8_H_6_N_4_)[Pt(C_2_H_8_N_2_)X]_2_X(ClO_4_)_3_\cdotH_2_O (X=Br,Cl) and (C_10_H_8_N_2_)[Pt(C_4_H_13_N_3_)Br]_2_Br_4_\cdot2H_2_O, comprising two-leg ladders of mixed-valent platinum ions, are described in terms of a multiband extended Peierls-Hubbard Hamiltonian. The polarized optical conductivity spectra are theoretically reproduced and the ground-state valence distributions are reasonably determined. The latter variety, whose interchain valence arrangement is out of phase, is reminiscent of conventional MX single-chain compounds, while the former variety, whose interchain valence arrangement is in phase, reveals itself as a novel d-p-\pi-hybridized multiband ladder material.

Competing ground states of a Peierls-Hubbard nanotube

Motivated by iodo platinum complexes assembled within a quadratic-prism lattice, [Pt(C2H8N2)(C10H8N2)I]4(NO3)8, we investigate the ground-state properties of a Peierls-Hubbard four-legged tube. Making a group-theoretical analysis, we systematically reveal a variety of valence arrangements, including half-metallic charge-density-wave states. Quantum and thermal phase competition is numerically demonstrated with particular emphasis on doping-induced successive insulator-to-metal transitions with conductivity increasing stepwise.

Nonlinear lattice relaxation of photoexcited diplatinum-halide chain compounds

Division of Physics, Hokkaido University, Sapporo 060-0810, Japan(Dated: 15 August 2005)In order to reveal the relaxation mechanism of photogenerated charge-transfer excitations inquasi-one-dimensional halogen-bridged diplatinum complexes, we calculate the low-lying adiabaticpotential energy surfaces of a one-dimensional extended Peierls-Hubbard model. High-energy excita-tions above the electron-hole continuum may relax into polarons, while excitons pumped within theoptical gap are self-localized and then either decay by luminescence or divide into solitons. Neutralsolitons, charged solitons, and polarons may be simultaneously photogenerated in a diplatinum-halide chain, which has never been observed in any conventional platinum-halide chain. Opticalconductivity is also simulated along the decay paths for experimental verification.

Photoinduced magnetic bound state in an itinerant correlated electron system with a spin-state degree of freedom

Photo-excited state in correlated electron system with spin-state degree of freedom is studied. We start from the two-orbital extended Hubbard model where energy difference between the two orbitals is introduced. Photo-excited metastable state is examined based on the effective model Hamiltonian derived by the two-orbital Hubbard model. Spin-state change is induced by photo-irradiation in the low-spin band insulator near the phase boundary. High-spin state is stabilized by creating a ferromagnetic bound state with photo-doped hole carriers. An optical absorption occurs between the bonding and antibonding orbitals inside of the bound state. Time-evolution for photo-excited states is simulated in the time-dependent mean-field scheme. Pair-annihilations of the photo-doped electron and hole generate the high-spin state in a low-spin band insulator. We propose that this process is directly observed by the time-resolved photoemission experiments.

Photoproduction of spin and charge carriers in halogen-bridged binuclear platinum chain complexes

Nonlinear lattice relaxation of photoexcited diplatinum-halide chain compounds is theoretically investigated within a one-dimensional extended Peierls–Hubbard model. We first illuminate the whole relaxation scenario in terms of variational wavefunctions and then visualize each relaxation channel numerically integrating the Schrodinger equation. High-energy excitations above the electron–hole continuum tend to relax into polarons, while excitons pumped within the optical gap, unless luminescent, turn into solitonic states nonradiatively. Neutral and charged solitons coexist as stable photoproducts, which has never been observed in conventional platinum-halide chains, and they are highly resonant on the occasion of their birth and geminate recombination.

Low-energy structure of the homometallic intertwining double-chain ferrimagnets A3Cu3(PO4)4 (A=Ca,Sr,Pb)

Motivated by the homometallic intertwining double-chain ferrimagnets

Soliton-induced optical absorption of halogen-bridged mixed-valence binuclear metal complexes

{A}_{3}{\mathrm{Cu}}_{3}{(\mathrm{P}{\mathrm{O}}_{4})}_{4}

Photoinduced Absorption Spectra of Halogen-bridged Binuclear Metal Complexes: Possible Contrast between R4[Pt2(P2O5H2)4X]·nH2O and Pt2(CH3CS2)4I

(A=\mathrm{Ca},\mathrm{Sr},\mathrm{Pb})

Optical manipulation of magnetism in spin-charge-coupled correlated electron systems

, we investigate the low-energy structure of their model Hamiltonian