1,602 research outputs found
USp(2k) Matrix Model: F Theory Connection
We present a zero dimensional matrix model based on with
supermultiplets in symmetric, antisymmetric and fundamental representations.
The four dimensional compactification of this model naturally captures the
exact results of Sen \cite{Sen} in theory. Eight dynamical and eight
kinematical supercharges are found, which is required for critical string
interpretation. Classical vacuum has ten coordinates and is equipped with
orbifold structure. We clarify the issue of spacetime dimensions which
theory represented by this matrix model produces.Comment: 11 pages, Latex: interpretation as large T^{6}/Z^{2} IIB orientifold
added, the final version to appear in Progress of Theoretical Physic
Current-induced persistent magnetization in a relaxorlike manganite
A single crystal of 7% Fe-doped
(LaPr)CaMnO shows up as a typical relaxor
ferromagnet, where ferromagnetic metallic and charge-orbital-ordered insulating
clusters coexist with controllable volume fraction by external stimuli. There,
the persistent ferromagnetic metallic state can be produced by an
electric-current excitation as the filamentary region, the magnetization in
which is increased by ~0.4 per Mn. A clear distinction from the
current heating effect in a magnetic field, which conversely leads to a
decrease in ferromagnetic fraction, enables us to bi-directionally switch both
the magnetization and resistance by applying the voltages with different
magnitudes.Comment: 4 pages, 3 figure
Dephasing in a quantum dot coupled to a quantum point contact
We investigate a dephasing mechanism in a quantum dot capacitively coupled to
a quantum point contact. We use a model which was proposed to explain the 0.7
structure in point contacts, based on the presence of a quasi-bound state in a
point contact. The dephasing rate is examined in terms of charge fluctuations
of electrons in the bound state. We address a recent experiment by
Avinun-Kalish {\it et al.} [Phys. Rev. Lett. {\bf 92}, 156801 (2004)], where a
double peak structure appears in the suppressed conductance through the quantum
dot. We show that the two conducting channels induced by the bound state are
responsible for the peak structure.Comment: 4 pages, 2 figure
Magnetic digital flop of ferroelectric domain with fixed spin chirality in a triangular lattice helimagnet
Ferroelectric properties in magnetic fields of varying magnitude and
direction have been investigated for a triangular-lattice helimagnet
CuFe1-xGaxO2 (x=0.035). The magnetoelectric phase diagrams were deduced for
magnetic fields along [001], [110], and [1-10] direction, and the in-plane
magnetic field was found to induce the rearrangement of six possible
multiferroic domains. Upon every 60-degree rotation of in-plane magnetic field
around the c-axis, unique 120-degree flop of electric polarization occurs as a
result of the switch of helical magnetic q-vector. The chirality of spin helix
is always conserved upon the q-flop. The possible origin is discussed in the
light of the stable structure of multiferroic domain wall.Comment: 5 pages, 4 figures. Accepted in Phys. Rev. Let
Field Effect Transistor Based on KTaO3 Perovskite
An n-channel accumulation-type field effect transistor (FET) has been
fabricated utilizing a KTaO3 single crystal as an active element and a
sputtered amorphous Al2O3 film as a gate insulator. The device demonstrated an
ON/OFF ratio of 10^4 and a field effect mobility of 0.4cm^2/Vs at room
temperature, both of which are much better than those of the SrTiO3 FETs
reported previously. The field effect mobility was almost temperature
independent down to 200K. Our results indicate that the Al2O3 / KTaO3 interface
is worthy of further investigations as an alternative system of future oxide
electronics.Comment: 3 pages, 3 Postscript figures, submitted to Appl.Phys.Let
Low temperature metallic state induced by electrostatic carrier doping of SrTiO
Transport properties of SrTiO-channel field-effect transistors with
parylene organic gate insulator have been investigated. By applying gate
voltage, the sheet resistance falls below 10 k at low
temperatures, with carrier mobility exceeding 1000 cm/Vs. The temperature
dependence of the sheet resistance taken under constant gate voltage exhibits
metallic behavior (/ 0). Our results demonstrate an insulator to
metal transition in SrTiO driven by electrostatic carrier density control.Comment: 3 pages, 4 figure
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