388 research outputs found
Electrostatically Controlled Magnetization Rotation in Ferromagnet-Topological Insulator Planar Structures
An approach to the electrostatic control of magnetization
rotation in the hybrid structures composed of topological insulators (TIs) and
adjacent ferromagnetic insulators (FMI) is proposed and studied. The concept is
based on TI electron energy variation with in-plane to put-of plane FMI
magnetization turn. The calculations explicitly expose the effect of free
energy variability in the form of the electrically controlled uniaxial magnetic
anisotropy, which depends on proximate exchange interaction and TI surface
electron density. Combining with inherent anisotropy, the magnetization
rotation from in-plane to out-of-plane direction is shown to be realizable for
1.7~2.7 ns under the electrical variation of TI chemical potential in the range
100 meV around Dirac point. When bias is withdrawn a small signal current
can target the out-of-plane magnetization instable state to the desirable
direction of in-plane easy axis, thus the structure can lay the foundation for
low energy nonvolatile memory prototype
Detecting -phase superfluids with -wave symmetry in a quasi-1D optical lattice
We propose an experimental protocol to study -wave superfluidity in a
spin-polarized cold Fermi gas tuned by an -wave Feshbach resonance. A
crucial ingredient is to add a quasi-1D optical lattice and tune the fillings
of two spins to the and band, respectively. The pairing order parameter
is confirmed to inherit -wave symmetry in its center-of-mass motion. We find
that it can further develop into a state of unexpected -phase modulation
in a broad parameter regime. Measurable quantities are calculated, including
time-of-flight distributions, radio-frequency spectra, and in situ
phase-contrast imaging in an external trap. The -phase -wave superfluid
is reminiscent of the -state in superconductor-ferromagnet
heterostructures but differs in symmetry and origin. If observed, it would
represent another example of -wave pairing, first discovered in He-3
liquids.Comment: 5 pages, 5 figure
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Direct Extrusion Freeforming of Ceramic Pastes
Microextrusion freeforming of ceramic lattices from high solids ceramic pastes provides
multi-scale hierarchical void structures with the advantages of low shrinkage stress and high
sintered density. Alumina lattices were directly fabricated using 80-500 Pm diameter filaments.
We report here on the implementation of design and fabrication of these scaffolds for band gap
materials and micro fluidic devices.Mechanical Engineerin
Small-Signal Amplification of Period-Doubling Bifurcations in Smooth Iterated Maps
Various authors have shown that, near the onset of a period-doubling
bifurcation, small perturbations in the control parameter may result in much
larger disturbances in the response of the dynamical system. Such amplification
of small signals can be measured by a gain defined as the magnitude of the
disturbance in the response divided by the perturbation amplitude. In this
paper, the perturbed response is studied using normal forms based on the most
general assumptions of iterated maps. Such an analysis provides a theoretical
footing for previous experimental and numerical observations, such as the
failure of linear analysis and the saturation of the gain. Qualitative as well
as quantitative features of the gain are exhibited using selected models of
cardiac dynamics.Comment: 12 pages, 7 figure
Stripe, checkerboard, and liquid-crystal ordering from anisotropic p-orbital Fermi surfaces in optical lattices
We study instabilities of single-species fermionic atoms in the p-orbital
bands in two-dimensional optical lattices at noninteger filling against
interactions. Charge density wave and orbital density wave orders with stripe
or checkerboard patterns are found for attractive and repulsive interactions,
respectively. The superfluid phase, usually expected of attractively
interacting fermions, is strongly suppressed. We also use field theory to
analyze the possible phase-transitions from orbital stripe order to
liquid-crystal phases and obtain the phase diagram. The condition of
nearly-perfect Fermisurface nesting, which is key to the above results, is
shown robustly independent of fermion fillings in such p-orbital systems, and
the momentum of density wave oscillation is highly tunable.
Such remarkable features show the promise of making those exotic orbital
phases, which are of broad interest in condensed-matter physics, experimentally
realizable with optical lattice gases.Comment: final version, 8 pages, 5 figure
Bose-Einstein supersolid phase for a novel type of momentum dependent interaction
A novel class of non-local interactions between bosons is found to favor a
crystalline Bose-Einstein condensation ground state. By using both low energy
effective field theory and variational wavefunction method, we compare this
state not only with the homogeneous superfluid, as has been done previously,
but also with the normal (non-superfluid) crystalline phase and obtain the
phase diagram. The key characters are: the interaction potential displays a
negative minimum at finite momentum which determines the wavevector of this
supersolid phase; and the wavelength corresponding to the momentum minimum
needs to be greater than the mean inter-boson distance.Comment: 4 pages 3 figures, fig 1 and fig 2 update
Radiation Mechanisms for Semiconductor Devices and Packages
VLSI semiconductor devices are often the source of radiated electromagnetic emissions from electronic devices. Noise coupled from these devices to resonant structures on the printed circuit board, resonant cables or resonant enclosures can result in EMI problems that are difficult or expensive to solve at the board or system level. This paper reviews three mechanisms by which noise can be coupled from semiconductor devices and packages resulting in radiated electromagnetic emissions
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