Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Opletal, P.; 酒井 宏典; 芳賀 芳範; 山本 悦嗣; 神戸 振作; 徳永 陽; 常盤 欣文
no journal, ,
Recently rediscovered orthorhombic UTe exhibits superconductivity at low temperatures below 2 K. The origin of superconductivity is still unknown even though its properties were investigated by different techniques and reported in literature. The origin of superconductivity could be found by investigating physical properties at temperatures above superconductivity. Existence of ferromagnetic fluctuations along the 
-axis was suggested based on thermodynamic and transport measurements while antiferromagnetic fluctuations were found by inelastic neutron scattering along the 
-axis. We investigate magnetic properties for all crystallographic axes in fields up to 7 T and temperature interval from 2 K up to 60 K. The obtained data are than evaluated by Maxwell relations between entropy and magnetization to obtain change of magnetic part of entropy in T-H diagram. The entropy for field along the -axis show ferromagnetic behavior with unusual behavior below ~ 7 K, while for field along the -axis we observe antiferromagnetic-like behavior. We discuss our results with consideration of results in literature and propose possible scenarios. The results obtained on superconducting sample are compared to non-superconducting
Opletal, P.; 酒井 宏典; 芳賀 芳範; 山本 悦嗣; 神戸 振作; 徳永 陽; 常盤 欣文
no journal, ,
Recently rediscovered orthorhombic UTe exhibits superconductivity at low temperatures below 2 K. The origin of superconductivity is still unknown even though its properties were investigated by different techniques and reported in literature. The origin of superconductivity could be found by investigating physical properties at temperatures above superconductivity. Existence of ferromagnetic fluctuations along the -axis was suggested based on thermodynamic and transport measurements while antiferromagnetic fluctuations were found by inelastic neutron scattering along the -axis. We investigate magnetic properties for all crystallographic axes in fields up to 7 T and temperature interval from 2 K up to 60 K. The obtained data are than evaluated by Maxwell relations between entropy and magnetization to obtain change of magnetic part of entropy in T-H diagram. The entropy for field along the -axis show ferromagnetic behavior with unusual behavior below ~ 7 K, while for field along the -axis we observe antiferromagnetic-like behavior. We discuss our results with consideration of results in literature and propose possible scenarios. The results obtained on superconducting sample are compared to non-superconducting
の格子欠陥が物性に及ぼす影響芳賀 芳範; Opletal, P.; 常盤 欣文; 山本 悦嗣; 徳永 陽; 神戸 振作; 酒井 宏典
no journal, ,
超伝導体UTeの単結晶を化学気相成長法により育成し、育成条件の違いが及ぼす影響を調べた。超伝導を示さない試料(NS)ではウランサイトの占有率が有意に減少していることを、EPMA組成分析及び単結晶X線構造解析により示した。欠損の影響は常伝導状態の電子比熱にも大きく影響を及ぼしており、これが超伝導の有無と関係している可能性がある。
studied by photoelectron spectroscopy藤森 伸一; 川崎 郁斗; 竹田 幸治; 山上 浩志; 仲村 愛*; 本間 佳哉*; 青木 大*
no journal, ,
The electronic structure of UTe was studied by resonant photoelectron spectroscopy (RPES) and angle-resolved photoelectron spectroscopy (ARPES) with soft X-ray synchrotron radiation. The partial U 5f density of states of UTe were imaged by the U~
-
RPES and it was found that the U~ state has an itinerant character, but there exists an incoherent peak due to the strong electron correlation effects. The band structure of UTe was obtained by ARPES and its overall band structure was mostly explained by band structure calculations, except for the incoherent band at 
eV. These results suggest that the U~ states of UTe have itinerant but strongly-correlated nature with enhanced hybridization with the Te~
states. In addition, the valence state of UTe was studied by core-level photoelectron spectroscopy. The main peak position of the U~
core-level spectrum of UTe coincides with that of UB, which is an itinerant compound with a nearly 
configuration. However, the main peak of UTe is broader than that of UB, and satellite structures are observed in the higher binding energy side of the main peak, which are characteristics of mixed-valence uranium compounds. These results suggest that the U~ state in UTe is in a mixed valence state with a dominant contribution from the itinerant 5
configuration.
の高純度単結晶における上部臨界磁場芳賀 芳範; 酒井 宏典; Opletal, P.; 常盤 欣文; 山本 悦嗣; 神戸 振作; 徳永 陽; 木俣 基*; 中村 慎太郎*; 淡路 智*; et al.
no journal, ,
特異な超伝導体UTeが国内外で大きな注目を集め、盛んに研究されているが既存試料は純度が低くその詳細は不明であった。本研究では、従来より飛躍的に純良な単結晶を用いて測定した上部臨界磁場の特徴を報告する。
-
phase diagram of spin-triplet superconducting UTe酒井 宏典
no journal, ,
スピン三重項超伝導体として注目されているUTeにおける新しい単結晶育成法を考案し、その条件最適化をおこなった結果、超伝導転移温度の向上に加えて、残留抵抗率比の大幅な改善がみられた。こうして得られた純良単結晶を用いて、電気抵抗率と交流帯磁率の同時測定を行なって強磁場25Tまでの磁場()-温度()相図の決定を行った。
高純度単結晶の強磁場磁気抵抗芳賀 芳範; 酒井 宏典; 常盤 欣文; Opletal, P.; 木俣 基*; 中村 慎太郎*; 淡路 智*; 佐々木 孝彦*; 青木 大*; 神戸 振作; et al.
no journal, ,
重い電子系UTeの高純度単結晶について強磁場磁気抵抗測定を行った。強磁場領域でシュブニコフ・ドハース振動が観測され、
でのフェルミ面極値断面積及び有効質量を決定し、
軸方向にのびた2次元フェルミ面を観測した。また、フェルミ面に起因する横磁気抵抗が観測され、キャリアの易動度に関する情報が得られ、重い電子の挙動に関する新たな情報が得られた。
; A Perspective from photoelectron spectroscopy藤森 伸一; 川崎 郁斗; 竹田 幸治; 山上 浩志; 仲村 愛*; 本間 佳哉*; 青木 大*
no journal, ,
The unconventional superconductors in 
-based materials attract much attention in recent years. Recently, it was discovered that UTe has relatively high transition temperature, and it is classified into one of such class of materials. In the present study, the electronic structure of UTe was studied by resonant photoelectron spectroscopy (RPES) and angle-resolved photoelectron spectroscopy (ARPES) with soft X-ray synchrotron radiation. The partial U 5 density of states of UTe were imaged by the U 4
-5 RPES and it was found that the U 5 state has an itinerant character, but there exists an incoherent peak due to the strong electron correlation effects. The band structure of UTe was obtained by ARPES and its overall band structure was mostly explained by band structure calculations, except for the incoherent band at 
eV. These results suggest that the U 5 states of UTe have itinerant but strongly-correlated nature with enhanced hybridization with the Te 5
states. The new ARPES data of the detailed electronic structure of Z point will be presented.
; A Perspective from photoelectron spectroscopy藤森 伸一
no journal, ,
The unconventional superconductors in -based materials attract much attention in recent years. Recently, it was discovered that UTe has relatively high transition temperature (
=1.65 K), and it is classified into one of such class of materials. In the present study, the electronic structure of UTe was studied by resonant photoelectron spectroscopy (RPES) and angle-resolved photoelectron spectroscopy (ARPES) with soft X-ray synchrotron radiation. The partial U 5 density of states of UTe2 were imaged by the U 4-5 RPES and it was found that the U 5 state has an itinerant character, but there exists an incoherent peak due to the strong electron correlation effects. The band structure of UTe was obtained by ARPES and its overall band structure was mostly explained by band structure calculations, except for the incoherent band at 
0.5 eV. These results suggest that the U 5 states of UTe have itinerant but strongly-correlated nature with enhanced hybridization with the Te 5 states.