Doping and temperature dependence of electron spectrum and quasiparticle dispersion in doped bilayer cuprates

Within the t-t'-J model, the electron spectrum and quasiparticle dispersion in doped bilayer cuprates in the normal state are discussed by considering the bilayer interaction. It is shown that the bilayer interaction splits the electron spectrum of doped bilayer cuprates into the bonding and antibonding components around the $(\pi,0)$ point. The differentiation between the bonding and antibonding components is essential, which leads to two main flat bands around the $(\pi,0)$ point below the Fermi energy. In analogy to the doped single layer cuprates, the lowest energy states in doped bilayer cuprates are located at the $(\pi/2,\pi/2)$ point. Our results also show that the striking behavior of the electronic structure in doped bilayer cuprates is intriguingly related to the bilayer interaction together with strong coupling between the electron quasiparticles and collective magnetic excitations.Comment: 9 pages, 4 figures, updated references, added figures and discussions, accepted for publication in Phys. Rev.

Novel kinetic models of xylan dissolution and degradation during ethanol based auto-catalyzed organosolv pretreatment of bamboo

Due to the invalidity of traditional models, pretreatment conditions dependent parameter of susceptible dissolution degree of xylan (dX) was introduced into the kinetic models. After the introduction of dX, the dissolution of xylan, and the formation of xylo-oligosaccharides and xylose during ethanol based auto-catalyzed organosolv (EACO) pretreatments of bamboo were well predicted by the pseudo first-order kinetic models (R2 > 97%). The parameter of dX was verified to be a variable dependent of EACO pretreatment conditions (such as solvent content in pretreatment liquor and pretreatment temperature). Based on the established kinetic models of xylan dissolution, the dissolution of glucan and the formation of degradation products (furfural and acetic acid) could also be empirically modeled (R2 > 97%). In addition, the relationship between xylan and lignin removal can provide guidance for alleviating the depositions of lignin or pseudo-lignin. The parameter of dX derived novel kinetic models can not only be used to reveal the multi-step reaction mechanisms of xylan, but also control the final removal of main components in bamboo during EACO pretreatments, indicating scientific and practical significance for governing the biorefinery of woody biomass

Pressure Effect on the superconducting properties of LaO_{1-x}F_{x}FeAs(x=0.11) superconductor

Diamagnetic susceptibility measurements under high hydrostatic pressure (up to 1.03 GPa) were carried out on the newly discovered Fe-based superconductor LaO_{1-x}F_{x}FeAs(x=0.11). The transition temperature T_c, defined as the point at the maximum slope of superconducting transition, was enhanced almost linearly by hydrostatic pressure, yielding a dT_c/dP of about 1.2 K/GPa. Differential diamagnetic susceptibility curves indicate that the underlying superconducting state is complicated. It is suggested that pressure plays an important role on pushing low T_c superconducting phase toward the main (optimal) superconducting phase.Comment: 7 pages, 4 figure

Nernst effect of the new iron-based superconductor LaO1−x_{1-x}Fx_{x}FeAs

We report the first Nernst effect measurement on the new iron-based superconductor LaO$_{1-x}$F$_{x}$FeAs $(x=0.1)$. In the normal state, the Nernst signal is negative and very small. Below $T_{c}$ a large positive peak caused by vortex motion is observed. The flux flowing regime is quite large compared to conventional type-II superconductors. However, a clear deviation of the Nernst signal from normal state background and an anomalous depression of off-diagonal thermoelectric current in the normal state between $T_{c}$ and 50 K are observed. We propose that this anomaly in the normal state Nernst effect could correlate with the SDW fluctuations.Comment: 8 pages, 4 figures; Latex file changed, references adde

Measurement of the branching fractions of psi(2S) -> 3(pi+pi-) and J/psi -> 2(pi+pi-)

Using data samples collected at sqrt(s) = 3.686GeV and 3.650GeV by the BESII detector at the BEPC, the branching fraction of psi(2S) -> 3(pi+pi-) is measured to be [4.83 +- 0.38(stat) +- 0.69(syst)] x 10^-4, and the relative branching fraction of J/psi -> 2(pi+pi-) to that of J/psi -> mu+mu- is measured to be [5.86 +- 0.19(stat) +- 0.39(syst)]% via psi(2S) -> (pi+pi-)J/psi, J/psi -> 2(pi+pi-). The electromagnetic form factor of 3(pi+pi-) is determined to be 0.21 +- 0.02 and 0.20 +- 0.01 at sqrt(s) = 3.686GeV and 3.650GeV, respectively.Comment: 17pages, 7 figures, submitted to Phys. Rev.