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竹島 由里子; 高橋 成雄*; 藤代 一成*; Nielson, G. M.*
Proceedings of IEEE Visualization 2004 (VIS 2004) (CD-ROM), 2 Pages, 2004/10
近年、可視化を用いたシミュレーションデータの解析が一般的に行われるようになってきた。計算機資源の発達などにより、シミュレーションデータは大規模化の一途をたどっており、これらを効率的に可視化するためには、あらかじめ与えられたシミュレーションデータの特徴解析を行い、その情報を用いて可視化処理を実行する必要がある。本研究では、データの特徴としてデータ分布の位相的変化に着目し、与えられたデータが持つ位相的特徴の定量化を行う。また、代表的な可視化手法であるボリュームレンダリングの色や不透明度を決定する伝達関数設計に位相的特徴量を利用し、データが持つ内部構造を明確に可視化する方法を提案する。さらに、本手法を実データに適用し、有効性を検証する。
Opletal, P.; 酒井 宏典; 常盤 欣文; 芳賀 芳範; 山本 悦嗣; 神戸 振作; 徳永 陽
no journal, ,
Magnetic semimetals are currently focus of research due to possible electronic topological features. Topological features originate from nontrivial band characters. One of the most interesting state is Weyl fermion which originate from band splitting driven by spin-orbit interaction due to the inversion symmetry breaking or time-reversal symmetry breaking. The materials with these properties are called Weyl semimetals. Wey fermions are expected to be robust and have high mobility, which is important for practical application of topological matter. Uranium materials are interesting candidates for Weyl semimetals because of their strong spin-orbit interaction causing band inversion and/or strong electronic correlations, often observed as 5f magnetism. One of the possible candidates are UOX (X = S, Se, Te) compounds. UOX (X = S, Se, Te) crystallizes in tetragonal PbFCl-type structure (P4/nmm space group). Only polycrystalline samples are reported in literature. UOS, UOSe and UOTe were reported to be antiferromagnets with T
= 55, 100 and 160 K, respectively. Magnetic structure of UOS and UOSe were reported to have moment along the c-axis with Q = (0, 0, 1/2). UOTe was theoretically predicted to have nontrivial topology. Recently we have prepared first single crystals of UOX (X = S, Se, Te) and shown they exhibit semimetallic conductivity. We will present the method of preparation of single crystals, results of magnetic, transport and thermal measurements and discuss these results in connection to Weyl semimetals.
Opletal, P.; 酒井 宏典; 常盤 欣文; 芳賀 芳範; 山本 悦嗣; 神戸 振作; 徳永 陽
no journal, ,
Uranium chalcogenides are large group of compounds showing different interesting properties. We will mainly discuss three different representatives: U
Te
, UOX (X= S, Se, Te) and UTe
. UTe recently gained large research interest due to discovery of unusual superconductivity and possible existence of topological spin-triplet conductivity. We managed to prepare highest quality of single crystals yet by molten salt growth method which shows almost doubled critical field for a-axis. To better understand superconductivity and physical properties of UTe we investigate change of magnetic property in magnetic field for all the crystallographic direction. We will compare and discuss our results on molten-salt grown sample UTe to results in literature. We will show that magnetic entropy at high temperatures, well above superconductivity, shows connection to superconducting properties. UOX (X= S, Se, Te) is group of antiferromagnets with high Neel temperature (80 K - 158 K). UOTe was predicted to be possibly Weyl semimetal. We prepared single crystal of these compounds by chemical vapor transport. All three compounds show semimetallic behavior with UOTe showing additional anomalies. We will present our results and discuss coexistence of small conductivity and high Neel temperature and possible non-trivial topological effects. UTe crystallizes in hexagonal structure P-6 with three different uranium positions and orders ferromagnetically at 48 K. It show additional increase of magnetization around 26 K in hard magnetic direction and behaves as semimeta. We will present our results and discuss possible origin of additional ordering in hard magnetic direction based on crystal structure and its connection to semimetallic behavior. We want to show that uranium chalcogenides are large group in which different phenomena can be observed due to different level of localization of uranium 5f level states.
Opletal, P.; 酒井 宏典; 芳賀 芳範; 常盤 欣文; 山本 悦嗣; 神戸 振作; 徳永 陽
no journal, ,
Magnetic semimetals are currently focus of research due to possible electronic topological features. Topological features originate from nontrivial band characters. One of the most interesting state is Weyl fermion which originate from band splitting driven by spin-orbit interaction due to the inversion symmetry breaking or time-reversal symmetry breaking. The materials with these properties are called Weyl semimetals. Wey fermions are expected to be robust and have high mobility, which is important for practical application of topological matter. Uranium materials are candidates for Weyl semimetals due to their strong spin-orbit interaction causing band inversion and/or strong electronic correlations, often observed as 5f magnetism. One of the possible candidates are UOX (X = S, Se, Te) compounds. UOX (X = S, Se, Te) crystallizes in tetragonal PbFCl-type structure (P4/nmm space group). Only polycrystalline samples are reported in literature. UOS, UOSe and UOTe were reported to be antiferromagnets with T = 55, 100 and 160 K, respectively. Magnetic structure of UOS and UOSe were reported to have moment along the c-axis with Q = (0,0,1/2). UOS and UOSe were both reported to exhibit semiconducting behavior on polycrystalline samples. UOTe was theoretically predicted to have nontrivial topology. Recently we have prepared first single crystals of UOX (X = S, Se, Te) and shown they exhibit semimetallic conductivity in contrast to published literature. We will present the method of preparation of single crystals, results of magnetic, transport and thermal measurements and discuss these results in connection to Weyl semimetals and results published in literature.