Theoretical study for the superconducting state in nano-superconductors

纳米超导体超导态的理论研究

• 批准号: 16540304
• 负责人: KOYAMA Tomio
• 金额: $ 2.3万
• 依托单位: Tohoku University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 2004
• 资助国家: 日本
• 起止时间: 2004 至 2005
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-16540304/
• 关键词: high-Tc cuprates; 0-pi Josephson junction; nano-superconductors; quantum bit; d-dot; GL theory; 0-πジョセフソン効果; 酸化物高温超電導体; 固有ジョセフソン効果; ジョセフソンプラズマ; 量子2準位

In this research project we studied the Josephson effects in small complex systems composed of unconventional d-wave and conventional s-wave superconductors from viewpoints of both basic physics and quantum devise applications. When a d-wave superconductor with d(x^2-y^2)-symmetry of square shape is embedded in a s-wave superconducting matrix, the system forms a closed 0-π Josephson junction in which vortices with half-flux quanta appear spontaneously. We construct a theory describing the phase dynamics in this complex system. When the size of the system is small enough, the quantum fluctuations dominate the system. We rigorously prove that this system behaves as a quantum two-level system in the quantum regime. The qubit applications were discussed. In this research project we also investigated the intrinsic Josephson effect observed in Bi-2212 high temperature superconductor. The origin of unusual field dependence of the microwave resonance absorption spectrum observed in Bi-2212 under a magnetic field parallel to the layers was clarified. The I-V characteristics and terahertz emission in a stack of intrinsic Josephson junctions were also discussed.

在这个研究项目中，我们从基础物理和量子器件应用的角度研究了由非常规 d 波和常规 s 波超导体组成的小型复杂系统中的约瑟夫森效应。 ^2)-正方形对称性嵌入s波超导矩阵中，系统形成一个封闭的0-π约瑟夫森结，其中存在半通量量子涡旋我们构建了一个描述该复杂系统中的相动力学的理论，当系统的尺寸足够小时，量子涨落在该系统中占主导地位。在本研究项目中，我们还研究了 Bi-2212 高温超导体中观察到的平行磁场下微波共振吸收光谱的异常场依赖性的起源。到还讨论了本征约瑟夫森结堆叠中的 I-V 特性和太赫兹发射。

项目成果

Structure of magnetic flux in nano-scaled superconductors

纳米级超导体中的磁通量结构

• 发表时间: 2004
• 期刊: J.Mag.Mag.Matter. 272-276
• 作者: H.Ishihara;H.Mifune;Masahiko Machida;J.Igarashi;M.Kato
• 通讯作者: M.Kato

Ginzuburg-Landau calculations of d-wave superconductng dot in s-wave superconducting matrix

s波超导矩阵中d波超导点的Ginzuburg-Landau计算

• 发表时间: 2004
• 期刊: Physica C 412-414
• 作者: J.Igarashi;T.Nomura;M.Takahashi;H.Suematsu;T.Nagao;T.Nagao;M.Kato
• 通讯作者: M.Kato

Quasi-particle spectrum of nano-scale superconducting plate under a magnetic field

磁场下纳米级超导板的准粒子谱

• 发表时间: 2006
• 期刊: J.Phys.Chem.Solids 67
• 作者: M.Kato;T.Koyama;M.Machida;T.Ishida
• 通讯作者: T.Ishida

Direct numerical simulations on non-equilibrium superconducting dynamics after neutron capture in MgB2

MgB2 中子俘获后非平衡超导动力学的直接数值模拟

• 发表时间: 2006
• 期刊: Nucl. Instr. and Meth. A559
• 作者: S.Maekawa;T.Tohyama et al.;H.Onodera;H.Matsueda;S.Maekawa 他;M.Kato;M.Machida
• 通讯作者: M.Machida

Phase Oscillation Modes of a Josephosn Vortex Lattice in Layered High-Tc Superconductors

层状高温超导体中约瑟夫涡旋晶格的相振荡模式

• 发表时间: 2004
• 期刊: Physica C 412-414
• 作者: J.Igarashi;T.Nomura;M.Takahashi;H.Suematsu;T.Nagao;T.Nagao;M.Kato;H.Matsumoto;M.Takahashi;M.Machida;T.Nagao;M.Machida;T.Koyama;T.Nomura;T.Koyama;J.Igarashi;M.Kato et al.;S.Suga;M.Machida et al.;J.Igarashi;T.Koyam
• 通讯作者: T.Koyam