Growth Dynamics of Photoinduced Domains in Two-Dimensional Charge-Ordered Conductors Depending on Stabilization Mechanisms

Photoinduced melting of horizontal-stripe charge orders in quasi-two-dimensional organic conductors \theta-(BEDT-TTF)2RbZn(SCN)4[BEDT-TTF=bis(ethylenedithio)tetrathiafulvalene] and \alpha-(BEDT-TTF)2I3 is investigated theoretically. By numerically solving the time-dependent Schr\"odinger equation, we study the photoinduced dynamics in extended Peierls-Hubbard models on anisotropic triangular lattices within the Hartree-Fock approximation. The melting of the charge order needs more energy for \theta-(BEDT-TTF)2RbZn(SCN)4 than for \alpha-(BEDT-TTF)2I3, which is a consequence of the larger stabilization energy in \theta-(BEDT-TTF)2RbZn(SCN)4. After local photoexcitation in the charge ordered states, the growth of a photoinduced domain shows anisotropy. In \theta-(BEDT-TTF)2RbZn(SCN)4, the domain hardly expands to the direction perpendicular to the horizontal-stripes. This is because all the molecules on the hole-rich stripe are rotated in one direction and those on the hole-poor stripe in the other direction. They modulate horizontally connected transfer integrals homogeneously, stabilizing the charge order stripe by stripe. In \alpha-(BEDT-TTF)2I3, lattice distortions locally stabilize the charge order so that it is easily weakened by local photoexcitation. The photoinduced domain indeed expands in the plane. These results are consistent with recent observation by femtosecond reflection spectroscopy.Comment: 9 pages, 8 figures, to appear in J. Phys. Soc. Jpn. Vol. 79 (2010) No.

Stochasticity, decoherence and an arrow of time from the discretization of time?

Certain intriguing consequences of the discreteness of time on the time evolution of dynamical systems are discussed. In the discrete-time classical mechanics proposed here, there is an {\it arrow of time} that follows from the fact that the replacement of the time derivative by the backward difference operator alone can preserve the non-negativity of the phase space density. It is seen that, even for free particles, all the degrees of freedom are {\it correlated} in principle. The forward evolution of functions of phase space variables by a finite number of time steps, in this discrete-time mechanics, depends on the entire continuous-time history in the interval $[0, \infty]$. In this sense, discrete time evolution is {\it nonlocal} in time from a continuous-time point of view. A corresponding quantum mechanical treatment is possible {\it via} the density matrix approach. The interference between non-degenerate quantum mechanical states decays exponentially. This {\it decoherence} is present, in principle, for all systems; however, it is of practical importance only in macroscopic systems, or in processes involving large energy changes.Comment: 10 pages, no figure

Alteration of Oral and Perioral Soft Tissue in Mice following Incisor Tooth Extraction

Oral and perioral soft tissues cooperate with other oral and pharyngeal organs to facilitate mastication and swallowing. It is essential for these tissues to maintain their morphology for efficient function. Recently, it was reported that the morphology of oral and perioral soft tissue can be altered by aging or orthodontic treatment. However, it remains unclear whether tooth loss can alter these tissues’ morphology. This study examined whether tooth loss could alter lip morphology. First, an analysis of human anatomy suggested that tooth loss altered lip morphology. Next, a murine model of tooth loss was established by extracting an incisor; micro-computed tomography revealed that a new bone replaced the extraction socket. Body weight was significantly lower in the tooth loss (UH) group than in the non-extraction control (NH) group. The upper lip showed a greater degree of morphological variation in the UH group. Proteomic analysis and immunohistochemical staining of the upper lip illustrated that S100A8/9 expression was higher in the UH group, suggesting that tooth loss induced lip inflammation. Finally, soft-diet feeding improved lip deformity associated with tooth loss, but not inflammation. Therefore, soft-diet feeding is essential for preventing lip morphological changes after tooth loss

Charge Order with Structural Distortion in Organic Conductors: Comparison between \theta-(ET)2RbZn(SCN)4 and \alpha-(ET)2I3

Charge ordering with structural distortion in quasi-two-dimensional organic conductors \theta-(ET)2RbZn(SCN)4 (ET=BEDT-TTF) and \alpha-(ET)2I3 is investigated theoretically. By using the Hartree-Fock approximation for an extended Hubbard model which includes both on-site and intersite Coulomb interactions together with Peierls-type electron-lattice couplings, we examine the role of lattice degrees of freedom on charge order. It is found that the experimentally observed, horizontal charge order is stabilized by lattice distortion in both compounds. In particular, the lattice effect is crucial to the realization of the charge order in \theta-(ET)2RbZn(SCN)4, while the peculiar band structure whose symmetry is lower than that of \theta-(ET)2RbZn(SCN)4 in the metallic phase is also an important factor in \alpha-(ET)2I3 together with the lattice distortion. For \alpha-(ET)2I3, we obtain a phase transition from a charge-disproportionated metallic phase to the horizontal charge order with lattice modulations, which is consistent with the latest X-ray experimental result.Comment: 10 pages, 13 figures, to appear in J. Phys. Soc. Jpn. Vol. 77 (2008) No.

Observation of the Dynamic Beta Effect at CESR with CLEO

Using the silicon strip detector of the CLEO experiment operating at the Cornell Electron-positron Storage Ring (CESR), we have observed that the horizontal size of the luminous region decreases in the presence of the beam-beam interaction from what is expected without the beam-beam interaction. The dependence on the bunch current agrees with the prediction of the dynamic beta effect. This is the first direct observation of the effect.Comment: 9 page uuencoded postscript file, postscritp file also available through http://w4.lns.cornell.edu/public/CLNS, submitted to Phys. Rev.

Observation of Radiative Decay D0→ϕγD^0 \to \phi \gamma

We report the observation of the decay $D^{0} \to \phi \gamma$ with a statistical significance of $5.4\sigma$ in 78.1 \ifb of data collected by the Belle experiment at the KEKB $e^+ e^-$ collider. This is the first observation of a flavor-changing radiative decay of a charmed meson. The Cabibbo- and color-suppressed decays $D^0 \to \phi \pi^0$, $\phi \eta$ are also observed for the first time. We measure branching fractions \br(D^{0} \to \phi \gamma) = [ 2.60^{+0.70}_{-0.61} \stat {}^{+0.15}_{-0.17} \syst ] \times 10^{-5}, \br(D^{0} \to \phi \pi^{0}) = [ 8.01 \pm 0.26 \stat \pm 0.47 \syst ] \times 10^{-4}, and \br(D^{0} \to \phi \eta) = [ 1.48 \pm 0.47 \stat \pm 0.09 \syst ] \times 10^{-4}.Comment: 9 pages, 4 figures, Belle Preprint 2003-24, KEK Preprint 2003-75, updated version of BELLE-CONF-0346 (contributed paper to the XXI International Symposium on Lepton and Photon Interactions at High Energies,Fermilab Aug 11-16,2003). to appear in Phys. Rev. Let

Measurement of Time-Dependent CP-Violating Asymmetries in B0→KsKsKsB_0 \to K_sK_sK_s Decay

We present a measurement of CP-violation parameters in the B0 -> KsKsKs decay based on a sample of 275 x 10^6 BBbar pairs collected at the Upsilon(4S) resonance with the Belle detector at the KEKB energy-asymmetric e+e- collider. One neutral B meson is fully reconstructed in the decay B0 -> KsKsKs, and the flavor of the accompanying B meson is identified from its decay products. CP-violation parameters are obtained from the asymmetry in the distributions of the proper-time interval between the two B decays: S = +1.26 +/- 0.68(stat) +/- 0.20(syst) and A = +0.54 +/- 0.34(stat) +/- 0.09(syst).Comment: 10 pages, 2 figures 10 pages, 2 figure

Measurements of Branching Fractions and CP Asymmetries in B-> etah Decays

We report measurements of B to pseudoscalar-pseudoscalar decays with at least one eta meson in the final state using 140 fb^{-1} of data collected by the Belle detector at KEKB e^+ e^- collider. We observe the decay B^+-> eta pi^+ and find evidence of B^+-> eta K+; the measured branching fractions are B(B^+-> eta pi^+)=(4.8^{+0.8}_{-0.7}(stat) +- 0.3(sys))*10^{-6} and B(B^+-> eta K^+)=(2.1 +- 0.6(stat)+- 0.2(sys))*10^{-6}. Their corresponding CP violating asymmetries are measured to be 0.07+- 0.15 (stat) +- 0.03(sys) for eta pi^+- and -0.49+- 0.31 (stat) +- 0.07(sys) for eta K^+-. No significant signals are found for neutral B->eta h decays. We report the following upper limits on branching fractions at the 90% confidence level: B(B-> eta K^0 < 2.0* 10^{-6}, B(B-> eta pi0) eta eta) <2.0*10^{-6}.Comment: 7 pages, 2 figure

Study of the suppressed B meson decay B^- -> D K^-, D -> K^+ \pi^-

We report a study of the suppressed B meson decay B^- -> D K^- followed by D -> K^+ \pi^-, where D indicates a D^0 or \bar{D}^0 state. The two decay paths interfere and provide information on the CP-violating angle \phi_3. We use a data sample containing 657 x 10^6 B\bar{B} pairs recorded at the \Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e^+e^- storage ring. We do not find significant evidence for the mode B^- -> D K^-, D -> K^+ \pi^-, and set an upper limit of r_B < 0.19, where r_B is the magnitude of the ratio of amplitudes |A(B^- -> \bar{D}^0 K^-)/A(B^- -> D^0 K^-)|. The decay B^- -> D \pi^-, D -> K^+ \pi^- is also analyzed as a reference, for which we observe a signal with 6.6\sigma significance, and measure the charge asymmetry A_{D\pi} to be -0.02^{+0.15}_{-0.16}(stat) \pm 0.04(syst). In addition, the ratio B(B^- -> D^0 K^-)/B(B^- -> D^0 \pi^-) is measured to be [6.77 \pm 0.23(stat) \pm 0.30(syst)] x 10^{-2}.Comment: 6 pages, 3 figures, 2 table