3,818 research outputs found
Lattice-form dependent orbital shape and charge disproportionation in charge- and orbital-ordered manganites
The orbital shapes and charge disproportionations at nominal Mn and
Mn sites for the charge- and orbital-ordered phases have been studied on
half-doped manganites Pr(SrCa)MnO and
EuCaMnO with double-layer and single-layer Mn-O networks,
respectively, by means of x-ray structural analyses, in comparison with
PrCaMnO with the pseudo cubic network. In a single-layer
EuCaMnO system, the ()/()-type orbital
shape is observed, while the ()/()-type orbital shape in a
pseudo cubic PrCaMnO system. In a double-layer
Pr(SrCa)MnO system, the orbital shape is found to
undergo a large change upon thermally induced rotation of orbital stripe.
Furthermore, clear charge disproportionation is observed for the pseudo cubic
and double-layer systems, while not in the single-layer system. These results
indicate that the orbital shape and charge disproportionation are sensitive to
the dimension of Mn-O network.Comment: 12 page, 5 figures, 11 table
Versatile helimagnetic phases under magnetic fields in cubic perovskite SrFeO3
A helical spin texture is of great current interest for a host of novel
spin-dependent transport phenomena. We report a rich variety of nontrivial,
helimagnetic phases in the simple cubic perovskite SrFeO3 under magnetic fields
up to 42 T. Magnetic and resistivity measurements revealed that the
proper-screw spin phase proposed for SrFeO3 can be subdivided into at least
five kinds of ordered phases. Near the multicritical point, an unconventional
anomalous Hall effect was found to show up and was interpreted as due to a
possible long-period noncoplanar spin texture with scalar spin chirality.Comment: 5 pages, 5 figures, Physical Review B in pres
Electrons doped in cubic perovskite SrMnO3: isotropic metal versus chainlike ordering of Jahn-Teller polarons
Single crystals of electron-doped SrMnO3 with a cubic perovskite structure
have been systematically investigated as the most canonical
(orbital-degenerate) double-exchange system, whose ground states have been
still theoretically controversial. With only 1-2% electron doping by Ce
substitution for Sr, a G-type antiferromagnetic metal with a tiny spin canting
in a cubic lattice shows up as the ground state, where the Jahn-Teller polarons
with heavy mass are likely to form. Further electron doping above 4%, however,
replaces this isotropic metal with an insulator with tetragonal lattice
distortion, accompanied by a quasi-one-dimensional 3z^2-r^2 orbital ordering
with the C-type antiferromagnetism. The self-organization of such dilute
polarons may reflect the critical role of the cooperative Jahn-Teller effect
that is most effective in the originally cubic system.Comment: 5 pages, 4 figure
All-optical transport and compression of ytterbium atoms into the surface of a solid immersion lens
We present an all-optical method to load 174Yb atoms into a single layer of
an optical trap near the surface of a solid immersion lens which improves the
numerical aperture of a microscope system. Atoms are transported to a region 20
um below the surface using a system comprised by three optical dipole traps.
The "optical accordion" technique is used to create a condensate and compress
the atoms to a width of 120 nm and a distance of 1.8 um away from the surface.
Moreover, we are able to verify that after compression the condensate behaves
as a two-dimensional quantum gas.Comment: 5 pages, 5 figure
Epitaxial-strain effect on charge/orbital order in Pr0.5Ca0.5MnO3 films
Effect of growth orientation on charge- and orbital-ordering (CO-OO)
phenomena has been studied for Pr0.5Ca0.5MnO3 epitaxial thin films fabricated
on (LaAlO3)0.3-(SrAl0.5Ta0.5O3)0.7 (LSAT) substrates by means of resistivity,
synchrotron x-ray diffraction, and polarized optical microscopy measurements.
CO-OO transition is observed around 220 K for a film grown on an LSAT (011)
substrate ((011)-film), similarly to a bulk sample, while a film grown on a
(001) plane of LSAT ((001)-film) shows much higher transition temperature
around 300 K. The domain size of OO is approximately 3 times as large in the
(011)-film as in the (001)-film. These results demonstrate that various
properties of CO-OO phenomena can be controlled with the growth orientation via
the epitaxial strain from the substrate.Comment: 4 pages, 4 figure
Enhanced quasiparticle heat conduction of the multigap superconductor Lu2Fe3Si5
The thermal transport measurements have been made on the Fe-based
superconductor Lu2Fe3Si5 (Tc ~ 6 K) down to a very low temperature Tc/120. The
field and temperature dependences of the thermal conductivity confirm the
multigap superconductivity with fully opened gaps on the whole Fermi surfaces.
In comparison to MgB2 as a typical example of the multigap superconductor in a
p-electron system, Lu2Fe3Si5 reveals a remarkably enhanced quasiparticle heat
conduction in the mixed state. The results can be interpreted as a consequence
of the electronic correlations derived from Fe 3d-electrons.Comment: 5 pages, 4 figure
Optical Aharonov-Bohm Effect on Wigner Molecules in Type-II Semiconductor Quantum Dots
We theoretically examine the magnetoluminescence from a trion and a biexciton
in a type-II semiconductor quantum dot, in which holes are confined inside the
quantum dot and electrons are in a ring-shaped region surrounding the quantum
dot. First, we show that two electrons in the trion and biexciton are strongly
correlated to each other, forming a Wigner molecule: Since the relative motion
of electrons is frozen, they behave as a composite particle whose mass and
charge are twice those of a single electron. As a result, the energy of the
trion and biexciton oscillates as a function of magnetic field with half the
period of the single-electron Aharonov-Bohm oscillation. Next, we evaluate the
photoluminescence. Both the peak position and peak height change
discontinuously at the transition of the many-body ground state, implying a
possible observation of the Wigner molecule by the optical experiment.Comment: 10 pages, 10 figures, accepted for publication in Phys. Rev.
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