4,177 research outputs found
NMR Evidence for Antiferromagnetic Transition in the Single-Component Molecular Conductor, [Au(tmdt)_{2}] at 110 K
We present the results of a ^{1}H NMR study of the single-component molecular
conductor, [Au(tmdt)_{2}].
A steep increase in the NMR line width and a peak formation of the nuclear
spin-lattice relaxation rate, 1/T_{1}, were observed at around 110 K.
This behavior provides clear and microscopic evidences for a magnetic phase
transition at considerably high temperature among organic conductors.
The observed variation in 1/T_{1} with respect to temperature indicates the
highly correlated nature of the metallic phase.Comment: 5pages, 6figures to be published in J. Phys. Soc. Jp
Direct evidence for ferromagnetic spin polarization in gold nanoparticles
We report the first direct observation of ferromagnetic spin polarization of
Au nanoparticles with a mean diameter of 1.9 nm using X-ray magnetic circular
dichroism (XMCD). Owing to the element selectivity of XMCD, only the gold
magnetization is explored. Magnetization of gold atoms estimated by XMCD shows
a good agreement with the results obtained by conventional magnetometry. This
result is evidence of intrinsic spin polarization in nano-sized gold.Comment: 4 pages, 3 figures, submitted to Phys. Rev. Let
Clinicopathologic features and histochemical analyses of proliferative activity and angiogenesis in small cell carcinoma of the esophagus
The original publication is available at www.springerlink.com.ArticleJOURNAL OF GASTROENTEROLOGY. 42(1-12): 932-938 (2007)journal articl
Quantum criticality around metal-insulator transitions of strongly correlated electrons
Quantum criticality of metal-insulator transitions in correlated electron
systems is shownto belong to an unconventional universality class with
violation of Ginzburg-Landau-Wilson(GLW) scheme formulated for symmetry
breaking transitions. This unconventionality arises from an emergent character
of the quantum critical point, which appears at the marginal point between the
Ising-type symmetry breaking at nonzero temperatures and the topological
transition of the Fermi surface at zero temperature. We show that Hartree-Fock
approximations of an extended Hubbard model on square latticesare capable of
such metal-insulator transitions with unusual criticality under a preexisting
symmetry breaking. The obtained universality is consistent with the scaling
theory formulated for Mott transition and with a number of numerical results
beyond the mean-field level, implying that the preexisting symmetry breaking is
not necessarily required for the emergence of this unconventional universality.
Examinations of fluctuation effects indicate that the obtained critical
exponents remain essentially exact beyond the mean-field level. Detailed
analyses on the criticality, containing diverging carrier density fluctuations
around the marginal quantum critical point, are presented from microscopic
calculations and reveal the nature as quantum critical "opalescence". Analyses
on crossovers between GLW type at nonzero temperature and topological type at
zero temperature show that the critical exponents observed in (V,Cr)2O3 and
kappa-ET-type organic conductor provide us with evidences for the existence of
the present marginal quantum criticality.Comment: 24 pages, 19 figure
Experimental observation of Frohlich superconductivity in high magnetic fields
Resistivity and irreversible magnetisation data taken within the
high-magnetic-field CDWx phase of the quasi-two-dimensional organic metal
alpha-(BEDT-TTF)2KHg(SCN)4 are shown to be consistent with a field-induced
inhomogeneous superconducting phase. In-plane skin-depth measurements show that
the resistive transition on entering the CDWx phase is both isotropic and
representative of the bulk.Comment: ten pages, four figure
Performance of Hamamatsu 64-anode photomultipliers for use with wavelength--shifting optical fibres
Hamamatsu R5900-00-M64 and R7600-00-M64 photomultiplier tubes will be used
with wavelength--shifting optical fibres to read out scintillator strips in the
MINOS near detector. We report on measurements of the gain, efficiency,
linearity, crosstalk, and dark noise of 232 of these PMTs, of which 219 met
MINOS requirements.Comment: 15 pages, 12 figures. Accepted by Nucl. Inst. Meth.
C NMR observation of a nonmagnetic charge-ordered state in the organic conductor -(ET)Hg(SCN)Cl
We investigated the local magnetism of the organic conductor,
-(ET)Hg(SCN)Cl, with a quasi-triangular lattice of weakly
dimerized molecules through C NMR spectroscopy. The NMR spectra and
nuclear relaxation show that charge disproportionation occurs, associated with
the metal-insulator transition at 31 K. The relaxation rate indicates that the
paramagnetic spins in the insulating phase undergo a transition into a
spin-singlet ground state with the emergence of orphan spins, a possible
valence-bond-glass state. The present results are in high contrast to the
spin-cluster paramagnetism of the electric dipole-liquid candidate,
--(ET)Hg(SCN)Br, having nearly identical material
parameters. This fact indicates that these two systems are on the verge between
distinct phases in both charge and spin degrees of freedom; a spin-singlet
charge-ordered state versus a spin-active Mott insulating state, competing with
each other on a triangular lattice of dimerized sites
Electron correlation in FeSe superconductor studied by bulk-sensitive photoemission spectroscopy
We have investigated the electronic structures of recently discovered
superconductor FeSe by soft-x-ray and hard-x-ray photoemission spectroscopy
with high bulk sensitivity. The large Fe 3d spectral weight is located in the
vicinity of the Fermi level (EF), which is demonstrated to be a coherent
quasi-particle peak. Compared with the results of the band structure
calculation with local-density approximation, Fe 3d band narrowing and the
energy shift of the band toward EF are found, suggesting an importance of the
electron correlation effect in FeSe. The self energy correction provides the
larger mass enhancement value (Z^-1=3.6) than in Fe-As superconductors and
enables us to separate a incoherent part from the spectrum. These features are
quite consistent with the results of recent dynamical mean-field calculations,
in which the incoherent part is attributed to the lower Hubbard band.Comment: 8 pages, 5 figures, 1 talbl
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