2,181 research outputs found
Hybridization-induced superconductivity from the electron repulsion on a tetramer lattice having a disconnected Fermi surface
Plaquette lattices with each unit cell containing multiple atoms are good
candidates for disconnected Fermi surfaces, which are shown by Kuroki and Arita
to be favorable for spin-flucutation mediated superconductivity from electron
repulsion. Here we find an interesting example in a tetramer lattice where the
structure within each unit cell dominates the nodal structure of the gap
function. We trace its reason to the way in which a Cooper pair is formed
across the hybridized molecular orbitals, where we still end up with a T_c much
higher than usual.Comment: 4 pages, 6 figure
High temperature superconductivity in dimer array systems
Superconductivity in the Hubbard model is studied on a series of lattices in
which dimers are coupled in various types of arrays. Using fluctuation exchange
method and solving the linearized Eliashberg equation, the transition
temperature of these systems is estimated to be much higher than that of
the Hubbard model on a simple square lattice, which is a model for the high
cuprates. We conclude that these `dimer array' systems can generally
exhibit superconductivity with very high . Not only -electron systems,
but also -electron systems may provide various stages for realizing the
present mechanism.Comment: 4 pages, 9 figure
Proton NMR Chemical Shift Behavior of Hydrogen-Bonded Amide Proton of Glycine-Containing Peptides and Polypeptides as Studied by ab initio MO Calculation
Abstract: NMR chemical shifts of the amide proton of a supermolecule, an Nmethylacetamide hydrogen-bonded with a formamide, were calculated as functions of hydrogen-bond length RN…O and hydrogen-bond angles by FPT-GIAO method within the framework of HF/STO 6-31++G(d,p) ab initio MO method. The calculations explained reasonably the experimental data reported previously that the isotropic proton chemical shifts move downfield with a decrease in RN…O. Further, the behavior of proton chemical shift tensor components depending on the hydrogen-bond length and hydrogen-bond angle was discussed
Large- meson theory
We derive an effective Lagrangian for meson fields. This is done in the light-cone gauge for two-dimensional large-N_c QCD by using the bilocal auxiliary field method. The auxiliary fields are bilocal on light-cone space and their Fourier transformation determines the parton momentum distribution. As the first test of our method, the 't Hooft equation is derived from the effective Lagrangian
"Pudding mold" band drives large thermopower in NaCoO
In the present study, we pin down the origin of the coexistence of the large
thermopower and the large conductivity in NaCoO. It is revealed that
not just the density of states (DOS), the effective mass, nor the band width,
but the peculiar {\it shape} of the band referred to as the "pudding
mold" type, which consists of a dispersive portion and a somewhat flat portion,
is playing an important role in this phenomenon. The present study provides a
new guiding principle for designing good thermoelectric materials.Comment: 5 page
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