6,460 research outputs found
Power law velocity fluctuations due to inelastic collisions in numerically simulated vibrated bed of powder}
Distribution functions of relative velocities among particles in a vibrated
bed of powder are studied both numerically and theoretically. In the solid
phase where granular particles remain near their local stable states, the
probability distribution is Gaussian. On the other hand, in the fluidized
phase, where the particles can exchange their positions, the distribution
clearly deviates from Gaussian. This is interpreted with two analogies;
aggregation processes and soft-to-hard turbulence transition in thermal
convection. The non-Gaussian distribution is well-approximated by the
t-distribution which is derived theoretically by considering the effect of
clustering by inelastic collisions in the former analogy.Comment: 7 pages, using REVTEX (Figures are inculded in text body)
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Single-crystal growth and magnetic properties of the metallic molybdate pyrochlore Sm2Mo2O7
We have successfully grown cm3-size single crystals of the
metallic-ferromagnet Sm2Mo2O7 by the floating-zone method using an infrared-red
image furnace. The growth difficulties and the remedies found using a 2-mirror
image furnace are discussed. Magnetization studies along the three crystalline
axes of the compound are presented and discussed based on our recent proposal
of an ordered spin-ice ground state for this compoun
A Weil-Barsotti formula for Drinfeld modules
We study the group of extensions in the category of Drinfeld modules and
Anderson's t-modules, and we show in certain cases that this group can itself
be given the structure of a t-module. Our main result is a Drinfeld module
analogue of the Weil-Barsotti formula for abelian varieties. Extensions of
general t-modules are also considered, in particular extensions of tensor
powers of the Carlitz module. We motivate these results from various directions
and compare to the situation of elliptic curves.Comment: 20 pages, latex file. To appear in Journal of Number Theor
Josephson current in a normal-metal nanowire coupled to superconductor/ferromagnet/superconductor junction
We consider superconducting nanowire proximity coupled to superconductor /
ferromagnet / superconductor junction, where the magnetization penetrates into
superconducting segment in nanowire decaying as with site index and the decay length . We tune chemical
potential and spin-orbit coupling so that topological superconducting regime
hosting Majorana fermion is realized for long . We find that when
becomes shorter, zero energy state at the interface between superconductor and
ferromagnet splits into two away from zero energy. Accordingly, the behavior of
Josephson current is drastically changed due to this "zero mode-non-zero mode
crossover". By tuning the model parameters, we find an almost second-harmonic
current-phase relation, , with phase difference . Based
on the analysis of Andreev bound state (ABS), we clarify that current-phase
relation is determined by coupling of the states within the energy gap. We find
that the emergence of crossing points of ABS is a key ingredient to generate
dependence in current-phase relation. We further study both the
energy and dependence of pair amplitudes in the ferromagnetic region.
For long , odd-frequency spin-triplet -wave component is dominant. The
magnitude of the odd-frequency pair amplitude is enhanced at the energy level
of ABS.Comment: 13 pages, 17 figure
Theoretical study of resonant x-ray emission spectroscopy of Mn films on Ag
We report a theoretical study on resonant x-ray emission spectra (RXES) in
the whole energy region of the Mn white lines for three prototypical
Mn/Ag(001) systems: (i) a Mn impurity in Ag, (ii) an adsorbed Mn monolayer on
Ag, and (iii) a thick Mn film. The calculated RXES spectra depend strongly on
the excitation energy. At excitation, the spectra of all three systems
are dominated by the elastic peak. For excitation energies around , and
between and , however, most of the spectral weight comes from
inelastic x-ray scattering. The line shape of these inelastic ``satellite''
structures changes considerably between the three considered Mn/Ag systems, a
fact that may be attributed to changes in the bonding nature of the Mn-
orbitals. The system-dependence of the RXES spectrum is thus found to be much
stronger than that of the corresponding absorption spectrum. Our results
suggest that RXES in the Mn region may be used as a sensitive probe
of the local environment of Mn atoms.Comment: 9 pages, 11 figure
Photoemission Spectral Weight Transfer and Mass Renormalization in the Fermi-Liquid System LaSrTiO
We have performed a photoemission study of LaSrTiO near
the filling-control metal-insulator transition (MIT) as a function of hole
doping. Mass renormalization deduced from the spectral weight and the width of
the quasi-particle band around the chemical potential is compared with
that deduced from the electronic specific heat. The result implies that, near
the MIT, band narrowing occurs strongly in the vicinity of . Spectral
weight transfer occurs from the coherent to the incoherent parts upon
antiferromagnetic ordering, which we associate with the partial gap opening at
.Comment: 4 pages, 3 figure
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