15,492 research outputs found
Non-thermal origin of nonlinear transport across magnetically induced superconductor-metal-insulator transition
We have studied the effect of perpendicular magnetic fields and temperatures
on the nonlinear electronic transport in amorphous Ta superconducting thin
films. The films exhibit a magnetic field induced metallic behavior intervening
the superconductor-insulator transition in the zero temperature limit. We show
that the nonlinear transport in the superconducting and metallic phase is of
non-thermal origin and accompanies an extraordinarily long voltage response
time.Comment: 5 pages, 4 figure
Epitaxial growth and the magnetic properties of orthorhombic YTiO3 thin films
High-quality YTiO3 thin films were grown on LaAlO3 (110) substrates at low
oxygen pressures (<10-8 Torr) using pulsed laser deposition. The in-plane
asymmetric atomic arrangements at the substrate surface allowed us to grow
epitaxial YTiO3 thin films, which have an orthorhombic crystal structure with
quite different a- and b-axes lattice constants. The YTiO3 film exhibited a
clear ferromagnetic transition at 30 K with a saturation magnetization of about
0.7 uB/Ti. The magnetic easy axis was found to be along the [1-10] direction of
the substrate, which differs from the single crystal easy axis direction, i.e.,
[001].Comment: 14 pages, 4 figure
Growth Dynamics of Photoinduced Domains in Two-Dimensional Charge-Ordered Conductors Depending on Stabilization Mechanisms
Photoinduced melting of horizontal-stripe charge orders in
quasi-two-dimensional organic conductors
\theta-(BEDT-TTF)2RbZn(SCN)4[BEDT-TTF=bis(ethylenedithio)tetrathiafulvalene]
and
\alpha-(BEDT-TTF)2I3 is investigated theoretically. By numerically solving
the time-dependent Schr\"odinger equation, we study the photoinduced dynamics
in extended Peierls-Hubbard models on anisotropic triangular lattices within
the
Hartree-Fock approximation. The melting of the charge order needs more energy
for \theta-(BEDT-TTF)2RbZn(SCN)4 than for \alpha-(BEDT-TTF)2I3, which is a
consequence of the larger stabilization energy in \theta-(BEDT-TTF)2RbZn(SCN)4.
After local photoexcitation in the charge ordered states, the growth of a
photoinduced domain shows anisotropy. In \theta-(BEDT-TTF)2RbZn(SCN)4, the
domain hardly expands to the direction perpendicular to the horizontal-stripes.
This is because all the molecules on the hole-rich stripe are rotated in one
direction and those on the hole-poor stripe in the other direction. They
modulate horizontally connected transfer integrals homogeneously, stabilizing
the charge order stripe by stripe. In \alpha-(BEDT-TTF)2I3, lattice distortions
locally stabilize the charge order so that it is easily weakened by local
photoexcitation. The photoinduced domain indeed expands in the plane. These
results are consistent with recent observation by femtosecond reflection
spectroscopy.Comment: 9 pages, 8 figures, to appear in J. Phys. Soc. Jpn. Vol. 79 (2010)
No.
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