657 research outputs found
Spin transport through a single self-assembled InAs quantum dot with ferromagnetic leads
We have fabricated a lateral double barrier magnetic tunnel junction (MTJ)
which consists of a single self-assembled InAs quantum dot (QD) with
ferromagnetic Co leads. The MTJ shows clear hysteretic tunnel magnetoresistance
(TMR) effect, which is evidence for spin transport through a single
semiconductor QD. The TMR ratio and the curve shapes are varied by changing the
gate voltage.Comment: 4 pages, 3 figure
Novel ordering of an S = 1/2 quasi one-dimensional Ising-like anitiferromagnet in magnetic field
High-field specific heat measurements on BaCo2V2O8, which is a good
realization of an S = 1/2 quasi one-dimensional Ising-like antifferomagnet,
have been performed in magnetic fields up to 12 T along the chain and at
temperature down to 200 mK. We have found a new magnetic ordered state in the
field-induced phase above Hc ~ 3.9 T. We suggest that a novel type of the
incommensurate order, which has no correspondence to the classical spin system,
is realized in the field-induced phase.Comment: 4pages, 4figure
Coherent Manipulation of Individual Electron Spin in a Double Quantum Dot Integrated with a Micro-Magnet
We report the coherent manipulation of electron spins in a double quantum dot
integrated with a micro-magnet. We performed electric dipole spin resonance
experiments in the continuous wave (CW) and pump-and-probe modes. We observed
two resonant CW peaks and two Rabi oscillations of the quantum dot current by
sweeping an external magnetic field at a fixed frequency. Two peaks and
oscillations are measured at different resonant magnetic field, which reflects
the fact that the local magnetic fields at each quantum dot are modulated by
the stray field of a micro-magnet. As predicted with a density matrix approach,
the CW current is quadratic with respect to microwave (MW) voltage while the
Rabi frequency (\nu_Rabi) is linear. The difference between the \nu_Rabi values
of two Rabi oscillations directly reflects the MW electric field across the two
dots. These results show that the spins on each dot can be manipulated
coherently at will by tuning the micro-magnet alignment and MW electric field.Comment: 5 pages, 3 figure
Ferromagnetism at the surface of a LaCoO3 single crystal observed using scanning SQUID microscopy
Evidence for ferromagnetism at the surface of a LaCo O3 single crystal is reported using a scanning superconducting quantum interference device (SQUID) microscope. Stray magnetic flux detected with the scanning SQUID shows typical ferromagnetic behavior in LaCo O3 below Tc ∼85 K, in agreement with previous work on LaCo O3 particles. Analysis of the magnetization of LaCo O3 particle samples clearly shows that the magnetization is inversely proportional to the particle radius, giving the information that the ferromagnetism is restricted within a few unit cell layers from the surface. X-ray photoemission spectroscopy also indicates that the ferromagnetism likely originates from the metallic surface due to hole doping with oxygen chemisorption
Longitudinal SDW order in a quasi-1D Ising-like quantum antiferromagnet
From neutron diffraction measurements on a quasi-1D Ising-like Co
spin compound BaCoVO, we observed an appearance
of a novel type of incommensurate ordering in magnetic fields. This ordering is
essentially different from the N{\' e}el-type ordering, which is expected for
the classical system, and is caused by quantum fluctuation inherent in the
quantum spin chain. A Tomonaga-Luttinger liquid (TLL) nature characteristic of
the gapless quantum 1D system is responsible for the realization of the
incommensurate ordering.Comment: 4pages, 4figur
Universality and superiority in preference for chromatic composition of art paintings
Color composition in paintings is a critical factor affecting observers' aesthetic judgments. We examined observers' preferences for the color composition of Japanese and Occidental paintings when their color gamut was rotated. In the experiment, observers were asked to select their preferred image from original and three hue-rotated images in a four-alternative forced choice paradigm. Despite observers' being unfamiliar with the presented artwork, the original paintings (0 degrees) were preferred more frequently than the hue-rotated ones. Furthermore, the original paintings' superiority was observed when the images were divided into small square pieces and their positions randomized (Scrambled condition), and when the images were composed of square pieces collected from different art paintings and composed as patchwork images (Patchwork condition). Therefore, the original paintings' superiority regarding preference was quite robust, and the specific objects in the paintings associated with a particular color played only a limited role. Rather, the original paintings' general trend in color statistics influenced hue-angle preference. Art paintings likely share common statistical regulations in color distributions, which may be the basis for the universality and superiority of the preference for original paintings.- We thank Dr. Yukinori Misaki at Kagawa National Institute of Technology, Japan and Ms. Nobuyo Okada and Ms. Kanako Maruchi at Toyohashi City Museum of Art and History, Japan for assisting in the measurement of art paintings. This work was supported by JSPS KAKENHI Grant Number JP19H01119 and 20H05956, and by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UIDB/04650/2020
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