1,361 research outputs found
Intergrowth and thermoelectric properties in the Bi-Ca-Co-O system
Single crystals of the Bi-Ca-Co-O system have been grown using the flux
method with cooling from 900\celsius and 950\celsius, respectively. The
single crystals are characterized by transmission electron microscopy and X-ray
diffraction. The misfit cobaltite
[CaBiCoO][CoO] single crystals with
quadruple (=4) rocksalt (RS) layer are achieved with cooling from
900\celsius. Such crystal exhibits room-temperature thermoelectric power
(TEP) of 180V/K, much larger than that in Sr-based misfit cobaltites with
quadruple RS layer. However, intergrowth of single crystals of quadruple
(=4) and triple (=3) RS-type layer-based misfit cobaltites is observed
with cooling from 950\celsius. Both of TEP and resistivity were obviously
enhanced by the intergrowth compared to
[CaBiCoO][CoO] single crystal,
while the power factor at room temperature remains unchanged.Comment: 8 pages, 7 figures. To be published in Journal of Crystal Growt
Extended Feynman Formula for the Harmonic Oscillator by the Discrete Time Method
We calculate the Feynman formula for the harmonic oscillator beyond and at
caustics by the discrete formulation of path integral. The extension has been
made by some authors, however, it is not obtained by the method which we
consider the most reliable regularization of path integral. It is shown that
this method leads to the result with, especially at caustics, more rigorous
derivation than previous.Comment: 9 page
Exchange Gate on the Qudit Space and Fock Space
We construct the exchange gate with small elementary gates on the space of
qudits, which consist of three controlled shift gates and three "reverse"
gates. This is a natural extension of the qubit case.
We also consider a similar subject on the Fock space, but in this case we
meet with some different situation. However we can construct the exchange gate
by making use of generalized coherent operator based on the Lie algebra su(2)
which is a well--known method in Quantum Optics. We moreover make a brief
comment on "imperfect clone".Comment: Latex File, 12 pages. I could solve the problems in Sec. 3 in the
preceding manuscript, so many corrections including the title were mad
Thermoelectric properties of the layered Pd oxide R_2PdO_4 (R = La, Nd, Sm and Gd)
We prepared polycrystalline samples of RPdO (R = La, Nd, Sm and Gd)
using a NaCl-flux technique. The measured resistivity is of the order of
10 cm at room temperature, which is two orders of magnitude
smaller than the values reported so far. We further studied the substitution
effects of Ce for Nd in NdCePdO, where the substituted Ce
decreases the resistivity and the magnitude of the thermopower. The activation
energy gap of 70-80 meV and the effective mass of 15 evaluated from the
measured data are suitable for thermoelectric materials, but the mobility of
10 cm/Vs is much lower than a typical value of 1-10 cm/Vs for
other thermoelectric oxides.Comment: 5 pages, 5 figures, to appear in J. Phys. Soc. Jp
Experimental Signature of Medium Modifications for rho and omega Mesons in the 12 GeV p + A Reactions
The invariant mass spectra of e+e- pairs produced in 12-GeV proton-induced
nuclear reactions are measured at the KEK Proton-Synchrotron. On the low-mass
side of the omega meson peak, a significant enhancement over the known hadronic
sources has been observed. The mass spectra, including the excess, are well
reproduced by a model that takes into account the density dependence of the
vector meson mass modification, as theoretically predicted.Comment: 4 pages, 3 figures, Version accepted for Physical Review Lette
Manipulating ionization path in a Stark map: Stringent schemes for the selective field ionization in highly excited Rb Rydberg atoms
We have developed a quite stringent method in selectivity to ionize the low
angular- momentum () states which lie below and above the adjacent
manifold in highly excited Rb Rydberg atoms. The method fully exploits the
pulsed field-ionization characteristics of the manifold states in high
slew-rate regime: Specifically the low state below (above) the adjacent
manifold is firstly transferred to the lowest (highest) state in the manifold
via the adiabatic transition at the first avoided crossing in low slew-rate
regime, and then the atoms are driven to a high electric field for ionization
in high slew-rate regime. These extreme states of the manifold are ionized at
quite different fields due to the tunneling process, resulting in thus the
stringent selectivity. Two manipulation schemes to realize this method actually
are demonstrated here experimentally.Comment: 10 pages, 4 figure
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