978 research outputs found
High-Field ESR Measurements of S=1/2 Kagome Lattice Antiferromagnet BaCuVO(OH)
High-field electron spin resonance (ESR) measurements have been performed on
vesignieite BaCuVO(OH), which is considered as a nearly ideal
model substance of =1/2 kagome antiferromagnet, in the temperature region
from 1.9 to 265 K. The frequency region is from 60 to 360 GHz and the applied
pulsed magnetic field is up to 16 T. Observed g-value and linewidth show the
increase below 20 K, which suggest the development of the short range order.
Moreover, a gapless spin liquid ground state is suggested from the
frequency-field relation at 1.9 K.Comment: 5 pages, 6 figures, jpsj2 class file, to be published in J. Phys.
Soc. Jp
Evolution of Elliptical Galaxies at z >~ 1 Revealed from a Large, Multicolor Sample of Extremely Red Objects
We study the evolution of elliptical galaxies at z >~ 1 on the basis of a
sample of 247 Extremely Red Objects (EROs) with R-Ks >= 3.35 (AB) and Ks <=
22.1 (AB) constructed from BVRi'z'JHKs multicolor data of a 114 arcmin2 area in
the Subaru/XMM Deep Survey Field. By fitting template spectra of old
ellipticals (OEs) and young, dusty starbursts (DSs) to the multicolor data, we
classify EROs into these two classes and estimate their redshifts. We find that
58% of the EROs in our sample belong to the OE class and that 24% of the OEs
are fit by a spectrum having a disk component with the B-band bulge-to-total
luminosity ratio of <= 0.9. We compare the observed surface density of OEs with
predictions from passive evolution models. We then derive rest-frame B-band
luminosity functions (LFs) of OEs in our sample at z=1-1.5 and 1.5-2.5. We find
that the LF at z=1-1.5 roughly agrees with the LF of local ellipticals if a
dimming of 1.3 mag from z=1.25 to the present epoch is assumed. On the other
hand, the amplitude of the LF at z=1.5-2.5 is found to be lower than that of
the local LF by a factor of ~ 3 over the whole range of magnitude observed.
Taking account of a strong decrease in the number density of morphologically
classified early-type galaxies at z >~ 1.5 found by several authors, we
conclude that the majority of ellipticals seen at present have not established
either a red color or a smooth 1/4-law profile before z ~ 1.5$. (abridged)Comment: 46 pages, 15 PostScript figures. Submitted to Ap
Small satellites with MEMS x-ray telescopes for x-ray astronomy and solar system exploration
Toward a new era of X-ray astronomy, next generation X-ray optics are indispensable. To meet a demand for telescopes lighter than the foil optics but with a better angular resolution less than 1 arcmin, we are developing micropore X-ray optics based on micromaching technologies. Using sidewalls of micropores through a thin silicon wafer, this type can be the lightest X-ray telescope ever achieved. Two new Japanese missions ORBIS and GEOX will carry this optics. ORBIS is a small X-ray astronomy mission to monitor supermassive blackholes, while GEO-X is a small exploration mission of the Earth's magnetosphere. Both missions need a ultra light-weight (<1 kg) telescope with moderately good angular resolution (<10 arcmin) at an extremely short focal length (<30 cm). We plan to demonstrate this optics in these two missions around 2020, aiming at future other astronomy and exploration missions
Experiments on Ladders Reveal a Complex Interplay between a Spin-Gapped Normal State and Superconductivity
In recent years, the study of ladder materials has developed into a
well-established area of research within the general context of Strongly
Correlated Electrons. This effort has been triggered by an unusual
cross-fertilization between theory and experiments. In this paper, the main
experimental results obtained in the context of ladders are reviewed from the
perspective of a theorist. Emphasis is given to the many similarities between
the two-dimensional high- cuprates and the two-leg ladder compounds,
including SrCaCuO (14-24-41) which has a
superconducting phase at high pressure and a small hole density. Examples of
these similarities include regimes of linear resistivity vs temperature in
metallic ladders and a normal state with spin-gap or pseudogap characteristics.
Some controversial results in this context are also discussed. It is remarked
that the ladder 14-24-41 is the first superconducting copper-oxide material
with a non-square-lattice layered arrangement, and certainly much can be
learned from a careful analysis of this compound. A short summary of the main
theoretical developments in this field is also included, as well as a brief
description of the properties of non-copper-oxide ladders. Suggestions by the
author on possible experiments are described in the text. Overall, it is
concluded that the enormous experimental effort carried out on ladders has
already unveiled quite challenging and interesting physics that adds to the
rich behavior of electrons in transition-metal-oxides, and in addition
contributes to the understanding of the two-dimensional cuprates. However,
still considerable work needs to be carried out to fully understand the
interplay between charge and spin degrees of freedom in these materials.Comment: Latex, 22 pages, with 41 GIF figures attache
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