17,848 research outputs found
Presence of 3d Quadrupole Moment in LaTiO3 Studied by 47,49Ti NMR
Ti NMR spectra of LaTiO3 are reexamined and the orbital state of this
compound is discussed. The NMR spectra of LaTiO3 taken at 1.5 K under zero
external field indicate a large nuclear quadrupole splitting. This splitting is
ascribed to the presence of the rather large quadrupole moment of 3d electrons
at Ti sites, suggesting that the orbital liquid model proposed for LaTiO3 is
inappropriate. The NMR spectra are well explained by the orbital ordering model
expressed approximately as originating from
a crystal field effect. It is also shown that most of the orbital moment is
quenched.Comment: 4 pages, 3 fugures; to appear in Phys. Rev. Let
Quantum oscillation of magnetoresistance in tunneling junctions with a nonmagnetic spacer
We make a theoretical study of the quantum oscillations of the tunneling
magnetoresistance (TMR) as a function of the spacer layer thickness. Such
oscillations were recently observed in tunneling junctions with a nonmagnetic
metallic spacer at the barrier-electrode interface. It is shown that momentum
selection due to the insulating barrier and conduction via quantum well states
in the spacer, mediated by diffusive scattering caused by disorder, are
essential features required to explain the observed period of oscillation in
the TMR ratio and its asymptotic value for thick nonmagnetic spacer.Comment: 4 pages, 5 figures, two column, REVTex4 styl
Novel Approach to Super Yang-Mills Theory on Lattice - Exact fermionic symmetry and "Ichimatsu" pattern -
We present a lattice theory with an exact fermionic symmetry, which mixes the
link and the fermionic variables. The staggered fermionic variables may be
reconstructed into a Majorana fermion in the continuum limit. The gauge action
has a novel structure. Though it is the ordinary plaquette action, two
different couplings are assigned in the ``Ichimatsu pattern'' or the checkered
pattern. In the naive continuum limit, the fermionic symmetry survives as a
continuum (or an ) symmetry. The transformation of the fermion is
proportional to the field strength multiplied by the difference of the two
gauge couplings in this limit. This work is an extension of our recently
proposed cell model toward the realization of supersymmetric Yang-Mills theory
on lattice.Comment: 26 pages, 4 figure
Low scale gravity mediation with warped extra dimension and collider phenomenology on the hidden sector
We propose a scenario of gravity mediated supersymmetry breaking (gravity
mediation) in a supersymmetric Randall-Sundrum model. In our setup, both of the
visible sector and the hidden sector co-exist on the infrared (IR) brane. We
introduce the Polonyi model as a simple hidden sector. Due to the warped
metric, the effective cutoff scale on the IR brane is ``warped down'', so that
the gravity mediation occurs at a low scale. As a result, the gravitino is
naturally the lightest superpartner (LSP) and contact interactions between the
hidden and the visible sector fields become stronger. We address
phenomenologies for various IR cutoff scales. In particular, we investigate
collider phenomenology involving a scalar field (Polonyi field) in the hidden
sector for the case with the IR cutoff around 10 TeV. We find a possibility
that the hidden sector scalar can be produced at the LHC and the International
Linear Collider (ILC). Interestingly, the scalar behaves like the Higgs boson
of the standard model in the production process, while its decay process is
quite different and, once produced, it will provide us with a very clean
signature. The hidden sector may be no longer hidden.Comment: 18 pages, 4 figures. typographical errors have been corrected and a
few new comments have been adde
Self-assembly of parallel atomic wires and periodic clusters of silicon on a vicinal Si(111) surface
Silicon self-assembly at step edges in the initial stage of homoepitaxial
growth on a vicinal Si(111) surface is studied by scanning tunneling microscopy
(STM). The resulting atomic structures change dramatically from a parallel
array of 0.7 nm wide wires to one dimensionally aligned periodic clusters of
the diameter ~ 2 nm and periodicity 2.7 nm in the very narrow range of growth
temperatures between 400 and 300 C. These nanostructures are expected to play
an important role in future development of silicon quantum computers.
Mechanisms leading to such distinct structures are discussed.Comment: Accepted for publication in Phys. Rev. Lett. Numbers of pages and
figures are 13 and 3, respectivel
Cut loci and conjugate loci on Liouville surfaces
In the earlier paper (Itoh and Kiyohara, Manuscr Math 114:247–264, 2004), we showed that the cut locus of a general point on two-dimensional ellipsoid is a segment of a curvature line and proved "Jacobi’s last geometric statement" on the singularities of the conjugate locus. In the present paper,we showthat a wider class of Liouville surfaces possess such simple cut loci and conjugate loci. The results include the determination of cut loci and the set of poles on two-sheeted hyperboloids and elliptic paraboloids
Tunnel magnetoresistance and interfacial electronic state
We study the relation between tunnel magnetoresistance (TMR) and interfacial
electronic states modified by magnetic impurities introduced at the interface
of the ferromagnetic tunnel junctions, by making use of the periodic Anderson
model and the linear response theory. It is indicated that the TMR ratio is
strongly reduced depending on the position of the -levels of impurities,
based on reduction in the spin-dependent -electron tunneling in the majority
spin state. The results are compared with experimental results for Cr-dusted
ferromagnetic tunnel junctions, and also with results for metallic multilayers
for which similar reduction in giant magnetoresistance has been reported.Comment: 5 pages, 4 figures, 2 column revtex4 format, ICMFS 2002 (Kyoto
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