6,883 research outputs found
Charge and spin collective modes in a quasi-1D model of Sr2RuO4
Given that Sr2RuO4 is a two-component p-wave superconductor, there exists the
possibility of well defined collective modes corresponding to fluctuations of
the relative phase and spin-orientation of the two components of the order
parameter. We demonstrate that at temperatures much below Tc, these modes have
energies small compared to the pairing gap scale if the superconductivity
arises primarily from the quasi 1D (dxz and dyz) bands, while it is known that
their energies become comparable to the pairing gap scale if there is a
substantial involvement of the quasi 2D (dxy) band. Therefore, the orbital
origin of the superconductivity can be determined by measuring the energies of
these collective modes.Comment: 11 pages (6 pages for main text), 2 figure
Experimental and analytical comparison of flowfields in a 110 N (25 lbf) H2/O2 rocket
A gaseous hydrogen/gaseous oxygen 110 N (25 lbf) rocket was examined through the RPLUS code using the full Navier-Stokes equations with finite rate chemistry. Performance tests were conducted on the rocket in an altitude test facility. Preliminary parametric analyses were performed for a range of mixture ratios and fuel film cooling pcts. It is shown that the computed values of specific impulse and characteristic exhaust velocity follow the trend of the experimental data. Specific impulse computed by the code is lower than the comparable test values by about two to three percent. The computed characteristic exhaust velocity values are lower than the comparable test values by three to four pct. Thrust coefficients computed by the code are found to be within two pct. of the measured values. It is concluded that the discrepancy between computed and experimental performance values could not be attributed to experimental uncertainty
Two Circular-Rotational Eigenmodes in Vortex Gyrotropic Motions in Soft Magnetic Nanodots
We found, by micromagnetic numerical and analytical calculations, that the
clockwise (CW) and counterclockwise (CCW) circular-rotational motions of a
magnetic vortex core in a soft magnetic circular nanodot are the elementary
eigenmodes existing in the gyrotropic motion with respect to the corresponding
CW and CCW circular-rotational-field eigenbasis. Any steady-state vortex
gyrotropic motions driven by a linearly polarized oscillating in-plane magnetic
field in the linear regime can be perfectly understood according to the
superposition of the two circular eigenmodes, which show asymmetric resonance
characteristics reflecting the vortex polarization. The relative magnitudes in
the amplitude and phase between the CCW and CW eigenmodes determine the
elongation and orientation of the orbital trajectories of the vortex core
motions, respectively, which trajectories vary with the polarization and
chirality of the given vortex as well as the field frequency across the
resonance frequency.Comment: 30 pages, 7 figure
Fundamental Limits to Coherent Photon Generation with Solid-State Atomlike Transitions
Coherent generation of indistinguishable single photons is crucial for many
quantum communication and processing protocols. Solid-state realizations of
two-level atomic transitions or three-level spin- systems offer
significant advantages over their atomic counterparts for this purpose, albeit
decoherence can arise due to environmental couplings. One popular approach to
mitigate dephasing is to operate in the weak excitation limit, where excited
state population is minimal and coherently scattered photons dominate over
incoherent emission. Here we probe the coherence of photons produced using
two-level and spin- solid-state systems. We observe that the coupling
of the atomic-like transitions to the vibronic transitions of the crystal
lattice is independent of driving strength and detuning. We apply a polaron
master equation to capture the non-Markovian dynamics of the ground state
vibrational manifolds. These results provide insight into the fundamental
limitations for photon coherence from solid-state quantum emitters, with the
consequence that deterministic single-shot quantum protocols are impossible and
inherently probabilistic approaches must be embraced.Comment: 16 pages [with supplementary information], 8 figure
Total Reflection and Negative Refraction of Dipole-Exchange Spin Waves at Magnetic Interfaces: Micromagnetic Modeling Study
We demonstrated that dipole-exchange spin waves traveling in geometrically
restricted magnetic thin films satisfy the same laws of reflection and
refraction as light waves. Moreover, we found for the first time novel wave
behaviors of dipole-exchange spin waves such as total reflection and negative
refraction. The total reflection in laterally inhomogeneous thin films composed
of two different magnetic materials is associated with the forbidden modes of
refracted dipole-exchange spin waves. The negative refraction occurs at a 90
degree domain-wall magnetic interface that is introduced by a cubic magnetic
anisotropy in the media, through the anisotropic dispersion of dipole-exchange
spin waves.Comment: 13 pages, 5 figure
Detecting the Majorana fermion surface state of He-B through spin relaxation
The concept of the Majorana fermion has been postulated more than eighty
years ago; however, this elusive particle has never been observed in nature.
The non-local character of the Majorana fermion can be useful for topological
quantum computation. Recently, it has been shown that the 3He-B phase is a
time-reversal invariant topological superfluid, with a single component of
gapless Majorana fermion state localized on the surface. Such a Majorana
surface state contains half the degrees of freedom of the single Dirac surface
state recently observed in topological insulators. We show here that the
Majorana surface state can be detected through an electron spin relaxation
experiment. The Majorana nature of the surface state can be revealed though the
striking angular dependence of the relaxation time on the magnetic field
direction, where is the angle between the
magnetic field and the surface normal. The temperature dependence of the spin
relaxation rate can reveal the gapless linear dispersion of the Majorana
surface state. We propose a spin relaxation experiment setup where we inject an
electron inside a nano-sized bubble below the helium liquid surface.Comment: 6 pages, 2 figures; reformatted with reference adde
Inverse Tunneling Magnetoresistance in nanoscale Magnetic Tunnel Junctions
We report on our theoretical study of the inverse TMR effect in the spin
polarized transport through a narrow channel. In the weak tunneling limit, we
find the ordinary positive TMR. The TMR changes its sign as the transmission
probability becomes large close to a unity. Our results might be relevant to
the magnetic tunnel junction with a pinhole or a quantum point contact.Comment: 11 pages, 4 figures, To be published in Phys. Rev. B (in press
Mandibular Fracture in Conjunction with Bicortical Penetration, Using Wide-Diameter Endosseous Dental Implants
Prosthodontic rehabilitation of a patient with an atrophic edentulous mandible presents a significant challenge in restoring esthetics and function. The purpose of this clinical report is to describe fracture of an atrophic edentulous mandible opposing maxillary natural dentition in association with endosseous dental implants. The patient received two wide-diameter implants in the anterior mandible for an implant-assisted mandibular overdenture, in which the implants penetrated the inferior border of the mandible for bicortical stabilization. Three months following implant placement surgery, the patient experienced pain, swelling, and intraoral purulent drainage around the right implant. Panoramic radiograph revealed a fracture of the mandible through the right implant site and signs of infection around the left implant. The implants were removed surgically, and open reduction and fixation of the fracture site were undertaken using a titanium bone fixation plate. This clinical report demonstrates that placement of wide-diameter implants in conjunction with bicortical penetration in a severely atrophic edentulous mandible can risk fracture of the mandible.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/79058/1/j.1532-849X.2010.00646.x.pd
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