p electron physics-Superconductivity and Magnetism in Borides and Carbides-

p电子物理学-硼化物和碳化物的超导性和磁性-

• 批准号: 15204033
• 负责人: AKIMITSU Jun
• 金额: $ 31.78万
• 依托单位: Aoyama Gakuin University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (A)
• 财政年份: 2003
• 资助国家: 日本
• 起止时间: 2003 至 2006
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-15204033/
• 关键词: Superconductivity; pelectron system; Y_2C_3; Tunneling spectroscopy; STM; 硼化物; 炭化物; 強磁性

This research project had aimed to elucidate the mechanism of superconductivity and magnetism in p electron system (borides, carbides, silicides ). We developed new superconducting materials and investigated the superconductivity in MgB2, NbB2, CaAISi, Y2C3 and magnetism in CaB6 from various experimental methods. The research results are listed as follows;1. We clarified that MgB2 is a new type strong coupling superconductor of which high energy phonon of light element plays an important role, because unusual temperature dependence of phonon density of states was observed at the energy range, corresponding to in B-plane phonon in MgB2 and Al-doped MgB2 probed by inelastic neutron scattering. From tunneling spectroscopy, we observed multi superconducting gaps which are correlated with each other.2. From the energy gap measurement by tunneling spectroscopy and MEM/Rietveld analysis using synchrotron X-ray in NbB2 and CaA1Si of which crystal structures are same with MgB2, we elucidate tha … More t these superconductors are considered to be strong coupling superconductors and have some correlation between superconducting properties and crystal structures in each system.3. We discovered new superconductors W_7Re_<13>X(X=B, C) (T_c=7.1 K, 7.3 K), Mo_7Re_<13>X(X=B, C) (T_c=8.3 K, 8.1 K) and Y_2C_3(T_c=18 K). The T_c of Y_2C_3 is changed from 11 K to 18 K by nominal composition and heat treatment. To elucidate the change of T_c in Y_2C_3 in terms of crystal structure, we performed crystal structure analysis and MEM/Rietveld analysis using synchrotron X-ray in detail. We clearly observed the forming C-C dimmer in Y_2C_3 and the evidence for correlation between Tc and the distance of C-C dimmer. From specific heat, ^<13>C-NMR and tunneling spectroscopy measurements, Y_2C_3 has two gaps in its superconducting state and each gap reveals the s-wave symmetry behavior. Especially, it is considered that the correlation between each gap is relatively small from the temperature dependence of each superconducting gap.4. We observed some phase transition of weak internal field at 150 K in temperature dependence of asymmetry of CaB_6 in μSR measurement. This behavior can not be ascribed to nuclear dipole field of B atoms. Moreover, a small electron pocket at Γ point was observed by ARPES (Angle Resolved Photo Emission Spectroscopy) using high quality single crystal of CaB_6. It is suggested that an unusual-magnetic behavior in CaB_6 is related to these results observed in μSR and ARPES measurements. Less

本研究旨在阐明p电子系统(硼化物、碳化物、硅化物)的超导电性和磁性机制。我们开发了新的超导材料，用各种实验方法研究了MgB_2、Nb_2、CaAl_3、Y_2C_3的超导电性和CaB_6的磁性。研究结果如下：1.阐明了MgB_2是一种新型的强耦合超导体，其中轻元素的高能声子起着重要的作用，因为在能量范围内观察到了声子态密度与温度的反常关系，对应于用非弹性中子散射探测到的镁B_2和掺铝镁B_2中的声子。从隧道光谱中，我们观察到多个相互关联的超导带隙。通过隧道谱测量和同步辐射X射线能隙分析，对晶体结构与…相同的NbB_2和CaAl_1Si进行了分析更多的超导体被认为是强耦合超导体，每个系统的超导性质与晶体结构之间存在一定的相关性。我们发现了新的超导体W_7Re_&lt；13&Gt；X(X=B，C)(T_c=7.1K，7.3K)，Mo_7Re_&lt；13&Gt；X(X=B，C)(T_c=8.3K，8.1K)和Y_2C_3(T_c=18K)。Y_2C_3的T_c随名义成分和热处理温度的变化从11 K变化到18 K。为了从晶体结构的角度阐明Y_2C_3中T_c的变化，我们用同步辐射X射线进行了详细的晶体结构分析和MEM/Rietveld分析。我们清楚地观察到了Y_2C_3中C-C二聚体的形成，并提供了T_c与C-C二聚体距离相关的证据。由比热、~(13)C-核磁共振和隧道谱测量，Y_2C_3在超导态有两个空隙，每个空隙都显示出S波的对称性。特别是从各超导带隙的温度依赖关系来看，各带隙之间的相关性相对较小。在μSR测量中，我们观察到了CaB6的非对称性随温度变化的150K弱内场相变。这种现象不能归因于B原子的核偶极场。此外，用高质量的CaB_6单晶用角度分辨光电子能谱(ARPES)观察到了Γ点的一个小电子口袋。这表明CaB_6的反常磁性行为与μSR和ARPES测量结果有关。较少

项目成果

Tunneling spectroscopy of deintercalated layered nitride superconductors ZrNCl_<0.7>

脱嵌层状氮化物超导体ZrNCl_<0.7>的隧道光谱

• 发表时间: 2005
• 期刊: J.Phys.Soc.Japan 74
• 作者: T.Ohnishi;T.Takasaki
• 通讯作者: T.Takasaki

Electrical resistivity and tunneling anomalies in CeCuAs_2

CeCuAs_2 中的电阻率和隧道异常

• 发表时间: 2005
• 期刊: Physica B 印刷中
• 作者: T.Ohnishi;T.Takasaki;T.Takasaki;R.A.Ribeiro;T.Takasaki;R.A.Ribeiro;E.V.Sampathkumaran
• 通讯作者: E.V.Sampathkumaran

Superconductivity in intermetallic compound Mo_7Re_<13>X(X=B,C)

金属间化合物Mo_7Re_<13>X(X=B,C)的超导性

• 发表时间: 2006
• 期刊: Science and Technology of Advanced Materials 7
• 作者: R.Nakamura;N.Hamada;H.Ichida;F.Tokunaga;Y.Kanematsu;K.Kawashima
• 通讯作者: K.Kawashima

Superconductivity in MgB_2 and Its Relate Materials

MgB_2及其相关材料的超导性

• 发表时间: 2005
• 期刊: Prog.Phys., Supplement No. 159
• 作者: Masahide Tanaka;Keiichi Tanaka;Hiromi Mitsuhashi;Tadafumi Akeno;Muneaki Hanawa;J.Akimitsu
• 通讯作者: J.Akimitsu

Electron tunneling experiments on La-substituted Kondo semiconductor CeRhAs

La取代近藤半导体CeRhAs的电子隧道实验

• 发表时间: 2006
• 期刊: Physica B (in press)
• 作者: S.Sasaki;H.Ikeda;K.Yamada;R.A.Ribeiro;T.Ekino;T.Ekino
• 通讯作者: T.Ekino