2,334 research outputs found
Cooper-Pair Spin Current in a Strontium Ruthenate Heterostructure
It has been recognized that the condensation of spin-triplet Cooper pairs
requires not only the broken gauge symmetry but also the spin ordering as well.
One consequence of this is the possibility of the Cooper-pair spin current
analogous to the magnon spin current in magnetic insulators, the analogy also
extending to the existence of the Gilbert damping of the collective
spin-triplet dynamics. The recently fabricated heterostructure of the thin film
of the itinerant ferromagnet SrRuO3 on the bulk Sr2RuO4, the best-known
candidate material for the spin-triplet superconductor, offers a promising
platform for generating such spin current. We will show how such
heterostructure allows us to not only realize the long-range spin valve but
also electrically drive the collective spin mode of the spin-triplet order
parameter. Our proposal represents both a new realization of the spin
superfluidity and a transport signature of the spin-triplet superconductivity.Comment: 5 pages, 3 figure
A serpentine laminating micromixer combining splitting/recombination and advection
Mixing enhancement has drawn great attention from designers of micromixers, since the flow in a microchannel is usually characterized by a low Reynolds number ( Re) which makes the mixing quite a difficult task to accomplish. In this paper, a novel integrated efficient micromixer named serpentine laminating micromixer (SLM) has been designed, simulated, fabricated and fully characterized. In the SLM, a high level of efficient mixing can be achieved by combining two general chaotic mixing mechanisms: splitting/recombination and chaotic advection. The splitting and recombination ( in other terms, lamination) mechanism is obtained by the successive arrangement of "F''-shape mixing units in two layers. The advection is induced by the overall three-dimensional serpentine path of the microchannel. The SLM was realized by SU-8 photolithography, nickel electroplating, injection molding and thermal bonding. Mixing performance of the SLM was fully characterized numerically and experimentally. The numerical mixing simulations show that the advection acts favorably to realize the ideal vertical lamination of fluid flow. The mixing experiments based on an average mixing color intensity change of phenolphthalein show a high level of mixing performance was obtained with the SLM. Numerical and experimental results confirm that efficient mixing is successfully achieved from the SLM over the wide range of Re. Due to the simple and mass producible geometry of the efficient micromixer, SLM proposed in this study, the SLM can be easily applied to integrated microfluidic systems, such as micro-total-analysis-systems or lab-on-a-chip systems.X11159165sciescopu
Disposable Integrated Microfluidic Biochip for Blood Typing by Plastic Microinjection Moulding
Blood typing is the most important test for both transfusion recipients and blood donors. In this paper, a low cost disposable blood typing integrated microfluidic biochip has been designed, fabricated and characterized. In the biochip, flow splitting microchannels, chaotic micromixers, reaction microchambers and detection microfilters are fully integrated. The loaded sample blood can be divided by 2 or 4 equal volumes through the flow splitting microchannel so that one can perform 2 or 4 blood agglutination tests in parallel. For the purpose of obtaining efficient reaction of agglutinogens on red blood cells (RBCs) and agglutinins in serum, we incorporated a serpentine laminating micromixer into the biochip, which combines two chaotic mixing mechanisms of splitting/recombination and chaotic advection. Relatively large area reaction microchambers were also introduced for the sake of keeping the mixture of the sample blood and serum during the reaction time before filtering. The gradually decreasing multi-step detection microfilters were designed in order to effectively filter the reacted agglutinated RBCs, which show the corresponding blood group. To achieve the cost-effectiveness of the microfluidic biochip for disposability, the biochip was realized by the microinjection moulding of COC (cyclic olefin copolymer) and thermal bonding of two injection moulded COC substrates in mass production with a total fabrication time of less than 20 min. Mould inserts of the biochip for the microinjection moulding were fabricated by SU-8 photolithography and the subsequent nickel electroplating process. Human blood groups of A, B and AB have been successfully determined with the naked eye, with 3 mu l of the whole sample bloods, by means of the fabricated biochip within 3 min.X11100104sciescopu
Electronic Manipulation of Magnon Topology by Chirality Injection from Boundaries
Magnon bands are known to exhibit nontrivial topology in ordered magnets
under suitable conditions, engendering topological phases referred to as
magnonic topological insulators. Conventional methods to drive a magnonic
topological phase transition are bulk magnetic or thermal operations such as
changing the direction of an external magnetic field or varying the temperature
of the system, which are undesired in device applications of magnon topology.
In this work, we lift the limitation of the magnon topology control on the bulk
non-electronic manipulation by proposing a scheme to manipulate magnonic
topological phases by electronic boundary operations of spin chirality
injection. More specifically, we consider a ferromagnetic honeycomb lattice and
show that a finite spin chirality injected from the boundary of the system via
the spin Hall effects introduces a tunable sublattice-symmetry-breaking mass
term to the bosonic counterpart of the Haldane model for the Chern insulators
and thereby allows us to electronically manipulate the bulk topology of magnons
from the boundary. The "shoulder" in the thermal Hall conductivity profile is
proposed as an experimental probe of the chirality-induced topological phase
transition. The scheme for the boundary manipulation of the magnon topology is
shown to work for a honeycomb antiferromagnet as well. We envisage that the
interfacial chirality injection may offer a nonintrusive electronic means to
tune the static and the dynamical bulk properties of general magnetic systems.Comment: 5 pages, 3 figure
Fractalized magnon transport on the quasicrystal with enhanced stability
Magnonics has been receiving significant attention in magnetism and
spintronics because of its premise for devices using spin current carried by
magnons, quanta of spin-wave excitations of a macroscopically ordered magnetic
media. Although magnonics has clear energy-wise advantage over conventional
electronics due to the absence of the Joule heating, the inherent magnon-magnon
interactions give rise to finite lifetime of the magnons which has been
hampering the efficient realizations of magnonic devices. To promote magnonics,
it is imperative to identify the delocalized magnon modes that are minimally
affected by magnon-magnon interactions and thus possess a long lifetime and use
them to achieve efficient magnon transport. Here, we suggest that quasicrystals
may offer the solution to this problem via the critical magnon modes that are
neither extended nor localized. We find that the critical magnon exhibits
fractal characteristics that are absent in conventional magnon modes in regular
solids such as a unique power-law scaling and a self-similar distribution of
distances showing perfect magnon transmission. Moreover, the critical magnons
have longer lifetimes compared to the extended ones in a periodic system, by
suppressing the magnon-magnon interaction decay rate. Such enhancement of the
magnon stability originates from the presence of the quasi-periodicity and
intermediate localization behavior of the critical magnons. Thus, we offer the
utility of quasicrystals and their critical spin wave functions in magnonics as
unique fractal transport characteristics and enhanced stability.Comment: 7 pages, 4 figure
Two-dimensional heterogeneous photonic bandedge laser
We proposed and realized a two-dimensional (2D) photonic bandedge laser
surrounded by the photonic bandgap. The heterogeneous photonic crystal
structure consists of two triangular lattices of the same lattice constant with
different air hole radii. The photonic crystal laser was realized by
room-temperature optical pumping of air-bridge slabs of InGaAsP quantum wells
emitting at 1.55 micrometer. The lasing mode was identified from its spectral
positions and polarization directions. A low threshold incident pump power of
0.24mW was achieved. The measured characteristics of the photonic crystal
lasers closely agree with the results of real space and Fourier space
calculations based on the finite-difference time-domain method.Comment: 14 pages, 4 figure
FlexRound: Learnable Rounding based on Element-wise Division for Post-Training Quantization
Post-training quantization (PTQ) has been gaining popularity for the
deployment of deep neural networks on resource-limited devices since unlike
quantization-aware training, neither a full training dataset nor end-to-end
training is required at all. As PTQ schemes based on reconstructing each layer
or block output turn out to be effective to enhance quantized model
performance, recent works have developed algorithms to devise and learn a new
weight-rounding scheme so as to better reconstruct each layer or block output.
In this work, we propose a simple yet effective new weight-rounding mechanism
for PTQ, coined FlexRound, based on element-wise division instead of typical
element-wise addition such that FlexRound enables jointly learning a common
quantization grid size as well as a different scale for each pre-trained
weight. Thanks to the reciprocal rule of derivatives induced by element-wise
division, FlexRound is inherently able to exploit pre-trained weights when
updating their corresponding scales, and thus, flexibly quantize pre-trained
weights depending on their magnitudes. We empirically validate the efficacy of
FlexRound on a wide range of models and tasks. To the best of our knowledge,
our work is the first to carry out comprehensive experiments on not only image
classification and natural language understanding but also natural language
generation, assuming a per-tensor uniform PTQ setting. Moreover, we
demonstrate, for the first time, that large language models can be efficiently
quantized, with only a negligible impact on performance compared to
half-precision baselines, achieved by reconstructing the output in a
block-by-block manner.Comment: Accepted to ICML 202
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