618 research outputs found
Observation of Current-induced Nonlinear Spin Polarization in Pt-Py Bilayers
We experimentally observe nonlinear spin polarization in metallic bilayers of
platinum and permalloy by means of spin-torque ferromagnetic resonance (ST-FMR)
with the spin-Hall effects. The ST-FMR results under massive dc current
injection contain striking features, which are not caused by extrinsic Joule
heating, but by intrinsic nonlinear spin polarization. The emergence of
nonlinear spin polarization is consistent with observation of unidirectional
spin-Hall magnetoresistance due to magnon generation/annihilation. Moreover,
the magnon generation (annihilation) leads to effective magnetization shrinkage
(expansion) revealed by the ST-FMR measurements. The present study paves a way
to spin-Hall effect based nonlinear spintronic devices as well as
6th-generation mobile communication light sources
Experimental investigation of pulsed entangled photons and photonic quantum channels
The development of key devices and systems in quantum information technology,
such as entangled particle sources, quantum gates and quantum cryptographic
systems, requires a reliable and well-established method for characterizing how
well the devices or systems work. We report our recent work on experimental
characterization of pulsed entangled photonic states and photonic quantum
channels, using the methods of state and process tomography. By using state
tomography, we could reliably evaluate the states generated from a two-photon
source under development and develop a highly entangled pulsed photon source.
We are also devoted to characterization of single-qubit and two-qubit photonic
quantum channels. Characterization of typical single-qubit decoherence channels
has been demonstrated using process tomography. Characterization of two-qubit
channels, such as classically correlated channels and quantum mechanically
correlated channels is under investigation. These characterization techniques
for quantum states and quantum processes will be useful for developing photonic
quantum devices and for improving their performances.Comment: 12 pages, 8 figures, in Quantum Optics in Computing and
Communications, Songhao Liu, Guangcan Guo, Hoi-Kwong Lo, Nobuyuki Imoto,
Eds., Proceedings of SPIE Vol. 4917, pp.13-24 (2002
Chiral meta-interface: Polarity reversal of ellipticity through double layers consisting of transparent chiral and absorptive achiral media
We have studied circular dichroism (CD) in the visible region of composite and double-layer films consisting of a transparent chiral molecule, glucose, and an absorptive achiral dye, rhodamine. Composite and double-layer films show an absorption-induced CD response caused by chirality of glucose at 540 nm, where the rhodamine exhibits absorption. More importantly, in double layers, the polarity of the ellipticity in CD signals is found to be reversed when the incident direction is reversed. We discuss the origin of the polarity reversal, which is very similar to the magneto-optical effect, at the chiral meta-interface without magnetic field
Direct Observation of Magnetochiral Effects through a Single Metamolecule in Microwave Regions
We report direct observation of magnetochiral (MCh) effects for the X-band microwaves through a single metamolecule consisting of a copper chiral structure and ferrite rod. A fictitious interaction between chirality and magnetism is realized in the metamolecule without intrinsic electronic interactions. The MCh effects are induced at the resonant optical activities by applying a weak dc magnetic field of 1 mT, and are increased with the magnetic field. The nonreciprocal differences in refractive indices are evaluated to be 10?3 at 200 mT
Metamaterials with magnetism and chirality
This review introduces and overviews electromagnetism in structured metamaterials which undergo simultaneous time-reversal and space-inversion symmetry breaking due to magnetism and chirality. Direct experimental observation of optical magnetochiral effects in a single metamolecule with magnetism and chirality is demonstrated at microwave frequencies. Numerical simulations based on a finite element method reproduce the experimental results well, and predict the emergence of giant magnetochiral effects, by combining resonances in the metamolecule. Toward the realization of magnetochiral effects at higher frequencies than microwaves, a metamolecule is miniaturized in the presence of ferromagnetic resonance in a cavity and coplanar waveguide. This work opens the door to the realization of a one-way mirror and synthetic gauge fields for electromagnetic waves
Observation of asymmetric electromagnetic field profiles in chiral metamaterials
We experimentally observe asymmetric electromagnetic field profiles along two-dimensional chiral metamaterials. The asymmetric field profiles depending on the chirality and the operation frequency have been reproduced well by the numerical simulation. Around a chiral meta-atom, distribution of a Poynting vector is found to be shifted asymmetrically. These results are explained in terms of an analogy with the side-jump mechanism in the electronic anomalous Hall systems
Pressure Study of BiS2-Based Superconductors Bi4O4S3 and La(O,F)BiS2
We report the electrical resistivity measurements under pressure for the
recently discovered BiS2-based layered superconductors Bi4O4S3 and La(O,F)BiS2.
In Bi4O4S3, the transition temperature Tc decreases monotonically without a
distinct change in the metallic behavior in the normal state. In La(O,F)BiS2,
on the other hand, Tc initially increases with increasing pressure and then
decreases above ? 1 GPa. The semiconducting behavior in the normal state is
suppressed markedly and monotonically, whereas the evolution of Tc is
nonlinear. The strong suppression of the semiconducting behavior without doping
in La(O,F)BiS2 suggests that the Fermi surface is located in the vicinity of
some instability. In the present study, we elucidate that the superconductivity
in the BiS2 layer favors the Fermi surface at the boundary between the
semiconducting and metallic behaviors.Comment: 4 pages, 6 figures, Accepted for publication in J. Phys. Soc. Jp
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