960 research outputs found
Photogenerated Carriers in SrTiO3 Probed by Mid-Infrared Absorption
Infrared absorption spectra of SrTiO have been measured under
above-band-gap photoexcitations to study the properties of photogenerated
carriers, which should play important roles in previously reported photoinduced
phenomena in SrTiO. A broad absorption band appears over the entire
mid-infrared region under photoexcitation. Detailed energy, temperature, and
excitation power dependences of the photoinduced absorption are reported. This
photo-induced absorption is attributed to the intragap excitations of the
photogenerated carriers. The data show the existence of a high density of
in-gap states for the photocarriers, which extends over a wide energy range
starting from the conduction and valence band edges.Comment: 5 pages, 5 figures, submitted to J. Phys. Soc. Jp
improving performance of feature extraction in sfm algorithms for 3d sparse point cloud
Abstract. The use of Structure-from-Motion algorithms is a common practice to obtain a rapid photogrammetric reconstruction. However, the performance of these algorithms is limited by the fact that in some conditions the resulting point clouds present low density. This is the case when processing materials from historical archives, such as photographs and videos, which generates only sparse point clouds due to the lack of necessary information in the photogrammetric reconstruction. This paper explores ways to improve the performance of open source SfM algorithms in order to guarantee the presence of strategic feature points in the resulting point cloud, even if sparse. To reach this objective, a photogrammetric workflow is proposed to process historical images. The first part of the workflow presents a method that allows the manual selection of feature points during the photogrammetric process. The second part evaluates the metric quality of the reconstruction on the basis of a comparison with a point cloud that has a different density from the sparse point cloud. The workflow was applied to two different case studies. Transformations of wall paintings of the Karanlık church in Cappadocia were analysed thanks to the comparison of 3D model resulting from archive photographs and a recent survey. Then a comparison was performed between the state of the Komise building in Japan, before and after restoration. The findings show that the method applied allows the metric scale and evaluation of the model also in bad condition and when only low-density point clouds are available. Moreover, this tool should be of great use for both art and architecture historians and geomatics experts, to study the evolution of Cultural Heritage
An 56Fe(d, p)57Fe Mossbauer Measurement
開始ページ、終了ページ: 冊子体のページ付
Fermionic response from fractionalization in an insulating two-dimensional magnet
Conventionally ordered magnets possess bosonic elementary excitations, called
magnons. By contrast, no magnetic insulators in more than one dimension are
known whose excitations are not bosons but fermions. Theoretically, some
quantum spin liquids (QSLs) -- new topological phases which can occur when
quantum fluctuations preclude an ordered state -- are known to exhibit Majorana
fermions as quasiparticles arising from fractionalization of spins. Alas,
despite much searching, their experimental observation remains elusive. Here,
we show that fermionic excitations are remarkably directly evident in
experimental Raman scattering data across a broad energy and temperature range
in the two-dimensional material -RuCl. This shows the importance of
magnetic materials as hosts of Majorana fermions. In turn, this first
systematic evaluation of the dynamics of a QSL at finite temperature emphasizes
the role of excited states for detecting such exotic properties associated with
otherwise hard-to-identify topological QSLs.Comment: 5 pages, 3 figure
Tc for heavy Fermion superconductors linked with other physical properties at zero and applied pressure
The superconducting transition temperature Tc has earlier been correlated
with coherence length and effective mass for a series of heavy Fermion (HF)
materials at atmospheric pressure. Here, a further physical property, the dc
electrical conductivity sigma(Tc), is one focal point, another being the
pressure dependence of both Tc and sigma(Tc) for several HF materials. The
relaxation time tau(Tc) is also studied in relation to an Uncertainty Principle
limit, involving only the thermal energy kB Tc and Planck's constant.Comment: Supercond. Sci. Tech., to appea
Ultrafast Photoinduced Formation of Metallic State in a Perovskite-type Manganite with Short Range Charge and Orbital Order
Femtosecond reflection spectroscopy was performed on a perovskite-type
manganite, Gd0.55Sr0.45MnO3, with the short-range charge and orbital order
(CO/OO). Immediately after the photoirradiation, a large increase of the
reflectivity was detected in the mid-infrared region. The optical conductivity
spectrum under photoirradiation obtained from the Kramers-Kronig analyses of
the reflectivity changes demonstrates a formation of a metallic state. This
suggests that ferromagnetic spin arrangements occur within the time resolution
(ca. 200 fs) through the double exchange interaction, resulting in an ultrafast
CO/OO to FM switching.Comment: 4 figure
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