STM Study on the Organic Superconductor

有机超导体的STM研究

• 批准号: 07454074
• 负责人: NOMURA Kazushige
• 金额: $ 4.99万
• 依托单位: HOKKAIDO UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 1995
• 资助国家: 日本
• 起止时间: 1995 至 1996
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07454074/
• 关键词: STM; Superconductivity; Tunneling Spectroscopy; Organic Metal; Superconducting Gap; 電子状態密度

We have developed the apparatus of the scanning tunneling microscope (STM) for the investigation of the electronic state of the organic superconductor and carried out the tunneling spectroscopy measurement with this apparatus. We have constructed the apparatus for the measurement under the magnitic field by combining the STM unit with the superconducting magnet. We have also performed the tunneling spectroscopic measurement in the superconducting phase of the organic superconductor (BEDT-TTF)_2Cu (NCS)_2For the construction of the STM apparatus, we purchased the STM unit and the superconducting solenoid and combined them with the possessed STM control unit. We also made the insert metal dewar for the tunneling unit. We have confirmed the operation of this apparatus up to the maximum field 7 T and down to the lowest temperature 1.4K in the preliminary measurement.We carried out the tunneling spectroscopic measurement on the organic superconductor (BEDT-TTF)_2Cu (NCS)_2 and investigated the anisotropy of the superconducting gap in the wave number space with changing the direction of surface of a single crystal sample. The obtained tunneling differential conductance clearly shows the superconducting gap structure and its functional form varies depending on the direction of the surface. It is understood that the electrons with the wave vector parallel to the tunneling tip direction dominantly contribute to the tunneling current in the STM spectroscopy measurement as well. At the same time it is clarified that the superconducting gap of (BEDT-TTF)_2Cu (NCS)_2 has a large anisotropy in the two-dimensional plane (b-c plane). It is indicated from the analysis of the angular dependence of the tunneling spectra that the superconducting gap has the d-wave symmetry where the gap disappears at the line on the Fermi surface. We are now progressing the STM measurement under the magnetic field.

我们研制了用于研究有机超导体电子态的扫描隧道显微镜(STM)装置，并用该装置进行了隧道光谱测量。我们将STM装置与超导磁体相结合，构成了磁场下的测量装置。我们还对有机超导体(BEDT-TTf)_2Cu(NCS)_2的超导相进行了隧道光谱测量。为了建造STM装置，我们购买了STM单元和超导螺线管，并将它们与已有的STM控制单元组合在一起。我们还制作了用于隧道掘进单元的镶嵌金属杜瓦。对有机超导体(BEDT-TTf)_2Cu(NCS)_2进行了隧道光谱测量，研究了超导带隙在波数空间随单晶表面方向变化的各向异性。得到的隧穿微分电导清楚地显示了超导带隙结构，其函数形式随表面方向的不同而变化。可以理解，在STM光谱测量中，波矢与隧道尖端方向平行的电子也是隧道电流的主要贡献者。同时阐明了(BEDT-TTf)_2Cu(NCS)_2的超导带隙在二维平面(b-c平面)上具有很大的各向异性。对隧道谱的角度依赖性分析表明，超导带隙具有d波对称性，在费米面上的直线处，带隙消失。我们现在正在进行磁场下的扫描隧道显微镜测量。

项目成果

K.Ichimura etal: "STM Spectroscopy of (BEDT-TTF)_2Cu(NCS)_2" Physica C. (印刷中). (1997)

K. Ichimura 等人：“(BEDT-TTF)_2Cu(NCS)_2 的 STM 光谱”Physica C.（出版中）。

A.Hoshikawa et al: "Sliding of the Spin-density Wave in (TMTSF)_2ClO_4" Synthetic Metals. (in press). (1997)

A.Hoshikawa 等人：“(TMTSF)_2ClO_4 中自旋密度波的滑动”合成金属。

N. Matsunaga et al.: "Anisotropic Magnetoresistance of (TMTSF)_2ClO_4 in the metallic and SDW state" Synthetic Metals. (発表予定). (1997)

N. Matsunaga 等人：“金属和 SDW 状态下 (TMTSF)_2ClO_4 的各向异性磁阻”合成金属（即将发表）。

K.Nomura et al.: "NMR Study on the Spin-density Wave Phase of (TMTSF)_2X" Synthetic Metals. (印刷中). (1997)

K. Nomura 等人：“(TMTSF)_2X 的自旋密度波相的核磁共振研究”（正在出版）。

N.Matsunaga et al.: "Influence of the Anion Disorder in the Organic Superconductor (TMTSF)_2ClO_4" Czechoslovak J.Phys.46Suppl.S2. 807-808 (1997)

N.Matsunaga 等人：“有机超导体 (TMTSF)_2ClO_4 中阴离子无序的影响”捷克斯洛伐克 J.Phys.46Suppl.S2。