17,247 research outputs found
Real Space Imaging of Spin Polarons in Zn Doped SrCu2(BO3)2
We report on the real space profile of spin polarons in the quasi
two-dimensional frustrated dimer spin system SrCu2(BO3)2 doped with 0.16% of
Zn. The 11B nuclear magnetic resonance spectrum exhibits 15 additional boron
sites near non-magnetic Zn impurities. With the help of exact diagonalizations
of finite clusters, we have deduced from the boron spectrum the distribution of
local magnetizations at the Cu sites with fine spatial resolution, providing
direct evidence for an extended spin polaron. The results are confronted with
those of other experiments performed on doped and undoped samples of
SrCu2(BO3)2.Comment: 9 pages, 11 figures, including supplemental materials. accepted for
publication in PR
Weak Phase gamma Using Isospin Analysis and Time Dependent Asymmetry in B_d -> K_s pi^+ pi^-
We present a method for measuring the weak phase gamma using isospin analysis
of three body B decays into K pi pi channels. Differential decay widths and
time dependent asymmetry in B_d -> K_s pi^+pi^- mode needs to be measured into
even isospin pi pi states. The method can be used to extract gamma, as well as,
the size of the electroweak penguin contributions. The technique is free from
assumptions like SU(3) or neglect of any contributions to the decay amplitudes.
By studying different regions of the Dalitz plot, it is possible to reduce the
ambiguity in the value of gamma.Comment: 11 pages, 1 figur
Electron-Transport Properties of Na Nanowires under Applied Bias Voltages
We present first-principles calculations on electron transport through Na
nanowires at finite bias voltages. The nanowire exhibits a nonlinear
current-voltage characteristic and negative differential conductance. The
latter is explained by the drastic suppression of the transmission peaks which
is attributed to the electron transportability of the negatively biased plinth
attached to the end of the nanowire. In addition, the finding that a voltage
drop preferentially occurs on the negatively biased side of the nanowire is
discussed in relation to the electronic structure and conduction.Comment: 4 pages, 6 figure
Influence of graft perfusion pressure on graft viability after small bowel preservation and transplantation
High-Tc superconductivity in entirely end-bonded multi-walled carbon nanotubes
We report that entirely end-bonded multi-walled carbon nanotubes (MWNTs) can
show superconductivity with the transition temperature Tc as high as 12K that
is approximately 40-times larger than those reported in ropes of single-walled
nanotubes. We find that emergence of this superconductivity is very sensitive
to junction structures of Au electrode/MWNTs. This reveals that only MWNTs with
optimal numbers of electrically activated shells, which are realized by the
end-bonding, can allow the superconductivity due to inter shell effects.Comment: 5 page
PMH76 COST ESTIMATION OF PSYCHIATRIC CARE IN THE JAPANESE HOSPITAL USING SYSTEM DYNAMICS SIMULATION
Pressure-induced Superconductivity in a Ferromagnet UGe -- Resistivity Measurements in Magnetic Field --
The electrical resistivity measurements in the magnetic field are carried out
on the pressure-induced superconductor UGe. The superconductivity is
observed from 1.06 to 1.44 GPa. The upper critical field of is
anisotropic where exhibits positive curvature for and
-axis. The characteristic enhancement of is reconfirmed for
-axis. In the temperature and field dependence of resistivity at where the ferromagnetic ordering disappears, it is observed that the
application of the external field along the {\it a}-axis increases the
coefficient of Fermi liquid behavior correspondingly to the
metamagnetic transition.Comment: To be published in the proceeding of the International Conference on
High Pressure Science and Technology(AIRAPT-18),Beijing,China,23-27 July 200
Measurement of CP Violation at the without Time Ordering or
I derive the expressions for the CP-violating asymmetry arising from
interference between mixed and direct decays in the Upsilon(4S) system, for the
case in which only one of the B decay times is observed, integrating over the
decay time of the other B. I observe that neither the difference of the decay
times Delta t, nor even their time-ordering, need be detected. A technique for
measurement of the CP-violating weak decay parameter sin(2beta) is described
which exploits this observation.Comment: 9 pages postscript, also available through
http://w4.lns.cornell.edu/public/CLN
Dynamical algebra and Dirac quantum modes in Taub-NUT background
The SO(4,1) gauge-invariant theory of the Dirac fermions in the external
field of the Kaluza-Klein monopole is investigated. It is shown that the
discrete quantum modes are governed by reducible representations of the o(4)
dynamical algebra generated by the components of the angular momentum operator
and those of the Runge-Lenz operator of the Dirac theory in Taub-NUT
background. The consequence is that there exist central and axial discrete
modes whose spinors have no separated variables.Comment: 17 pages, latex, no figures. Version to appear in Class.Quantum Gra
An effective spin-orbital Hamiltonian for the double perovskite SrFeW O: Derivation of the phase diagram
We formulate a superexchange theory of insulating double-perovskite compounds
such as SrFeWO. An effective spin-orbital Hamiltonian is derived in the
strong coupling limit of Hubbard model for d-electrons on Fe and W ions. The
relevant degrees of freedom are the spins S=2 and the three-fold orbital
degeneracy of Fe-ions. W-sites are integrated out by means of a
fourth-order perturbative expansion. The magnetically and orbitally ordered
ground states of the effective Hamiltonia n are discussed as a function of the
model parameters. We show that for realistic values of such parameters the
ground state is antiferromagnetic, as experimentally observed. The order found
is of type-II, consisting of \{111\} ferromagnetic planes stac ked
antiferromagnetically. The orbital order energy scale found is one order of
magnitude less than the spi n one.Comment: 12 pages, 4 figure
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