梯子型格子を持つ系の超伝導-その物性の解明と新しい系の探索

梯状晶格系统中的超导性 - 阐明其物理特性并寻找新系统

• 批准号: 10440113
• 负责人: AKIMITSU Jun
• 金额: $ 9.47万
• 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 (B)
• 财政年份: 1998
• 资助国家: 日本
• 起止时间: 1998 至 1999
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-10440113/
• 关键词: Superconductivity; Cu oxide; Ladder compound; Spin gap

Recently, the ladder system which consists of two coupled spin-1/2 chains was proposed as an interesting intermediate step between one-and two-dimensional systems. Dagotto et al. and Rice et. Al. predicted that hole-doping in a spin-ladder system might produce the metallic state with a spin gap and give rise to novel superconductivity.To examine the theoretical prediction, carrier doping to SrィイD214xィエD2CaィイD2xィエD2CuィイD224ィエD2OィイD241ィエD2, being composed of CuィイD22ィエD2OィイD23ィエD2 planes with two-leg ladders, has been performed. We discovered that heavily Ca-substituted compound (x=13.6) showed superconductivity under pressure (TィイD2cィエD2(onset)〜l2K at 3.5 Gpa). To discuss the superconductivity further, the single crystal measurements have been made. Superconductivity was observed between 3.5 Gpa and 8 Gpa (TィイD2cィエD2 (onset)〜9K at 4.5GPa), accompanied by metallic resistivity between the ladders. This results strongly suggests that the application of pressure brings about a crossover from … More one-to two-dimensional and the system is anisotropic two-dimensional at the optimum pressure for the superconducting transition.To discuss the relationship between spin gap and the superconductivity, we carried out the inelastic neutron scattering experiment for SrィイD22.5ィエD2CaィイD211.5ィエD2CuィイD224ィエD2OィイD241ィエD2 single crystal. The spin gap energy for the ladder is found to be 32.1meV and the exchange coupling was estimated to be 90 meV (along the ladders) and 65 meV (along the rung).Specific heat, magnetic susceptibility and neutron scattering measurements were performed on SrィイD214xィエD2CaィイD2xィエD2CuィイD224ィエD2OィイD241ィエD2 single crystals. The specific heat of Ca-substituted samples SrィイD214xィエD2CaィイD2xィエD2CuィイD224ィエD2OィイD241ィエD2 showed a sharp phase transition at about 3 K. By the measurements of the magnetic susceptibility, it was confirmed that the phase transition was originated from antiferromagnetic long-range order. Besides, the several magnetic Bragg peaks were observed by neutron scattering measurement, and a possible magnetic structure on the chain and ladder sites were determined. In this system, the singlet state and antiferromagnetic order induced by appropriate hole-doping coexist at ambient pressure. Less

最近，由两个耦合的自旋 1/2 链组成的梯子系统被提出作为一维和二维系统之间的一个有趣的中间步骤。达戈托等人。和赖斯等人。阿尔。预测自旋梯系统中的空穴掺杂可能会产生具有自旋间隙的金属态并产生新颖的超导性。为了检验理论预测，载流子掺杂到 SrィイD214xィエD2CaィイD2xィエD2CuィイD224ィエD2OィイD241ィエD2，由 CuィイD22ィエD2OィイD23ィエD2飞机与两腿梯子，已被执行。我们发现重度Ca取代的化合物(x=13.6)在压力下表现出超导性(TィイD2cィエD2(onset)〜l2K at 3.5 Gpa)。为了进一步讨论超导性，进行了单晶测量。在 3.5 Gpa 和 8 Gpa 之间观察到超导性（TィイD2cィエD2（开始）〜9K at 4.5GPa），并伴有梯子之间的金属电阻率。这一结果强烈表明，压力的施加带来了从一维到二维的交叉，并且系统在超导转变的最佳压力下是各向异性的二维。为了讨论自旋间隙与超导性之间的关系，我们进行了非弹性中子散射实验 SrィイD22.5ィエD2CaィイD211.5ィエD2CuィイD224ィエD2OィイD241ィエD2单晶。发现梯子的自旋间隙能量为 32.1meV，交换耦合估计为 90 meV（沿着梯子）和 65 meV（沿着梯级）。比热、磁化率和中子散射测量在 SrィイD214xィエD2CaィイD2xィエD2CuィイD224ィエD2OィイD241ィエD2单晶。 Ca取代样品SrィイD214xィエD2CaィイD2xィエD2CuィイD224ィエD2OィイD241ィエD2的比热在3 K左右表现出急剧的相变。通过磁化率的测量，证实相变源于反铁磁长程订单。此外，通过中子散射测量观察到了几个磁性布拉格峰，并确定了链和梯位上可能的磁性结构。在该系统中，由适当的空穴掺杂引起的单线态和反铁磁有序在环境压力下共存。较少的

项目成果

T.Nagata et al.: "Antiferromagnetic Ordering in the Spin Singlet State on that Ladder/Chain Material"J.Phys.Soc.Jpn. 68. 2206-2209 (1999)

T.Nagata 等人：“梯/链材料上自旋单重态的反铁磁有序”J.Phys.Soc.Jpn。

J.Akimitsu et al.: "Spin and Charge Dynamics in the Hole-Doped Two-Leg Ladder Compound SrィイD214-xィエD2CaィイD2xィエD2CuィイD224ィエD2OィイD241ィエD2"Phys.Chem.Trans.Met.Oxi.. 125. 289-298 (1999)

J.Akimitsu 等人：“空穴掺杂两腿梯形化合物 SrD214-xD2CaD2xD2CuD224D2OD241D2 中的自旋和电荷动力学”Phys.Chem.Trans.Met.Oxi.. 125. 289-298 (1999)

T. Nagata et al: "Antiferromagnetic Ordering in the Spin Singlet State on thet Ladder/Chain Material"J. Phys. Soc. Jpn.. Vol.68. 2206-2209 (1999)

T. Nagata 等人：“梯子/链材料上自旋单线态的反铁磁有序化”J。

T.tagata et al.: "Coexistence of the spin liquid state and the magnetic ordering in the spin ladder compound SrィイD214-xィエD2CaィイD2xィエD2CuィイD224ィエD2OィイD241ィエD2"J.Phys.Chem.Solids. 60. 1109-1111 (1999)

T.tagata 等人：“自旋梯化合物 SrD214-xD2CaD2xD2CuD224D2OD241D2 中自旋液态和磁有序的共存”J.Phys.Chem.Solids 60. 1109-1111 (1999)

M.Tamura et al.: "A new superconductor with 1222 structure (Cu_<1-x>M_x)Sr_2(Y_<1-y>Ce_y)_2Cu_2O_δ(M=Ti,V,Cr,Fe,Co,Ga,Ge,Mo,Ce,W and Re)" Physica C. Vol.33 No.1&2. 1-10 (1998)

M.Tamura等人：“一种具有1222结构的新型超导体 (Cu_<1-x>M_x)Sr_2(Y_<1-y>Ce_y)_2Cu_2O_δ(M=Ti,V,Cr,Fe,Co,Ga,Ge 、Mo、Ce、W 和 Re)”Physica C. Vol.33 No.1&2. 1-10 (1998)