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

最近，梯子系统的两对旋转-1/2链被提议作为一个和两个维度系统之间的一个有趣的中间步骤。Dagotto等人和Rice等人。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，car？doping to Sry D214x y D2Ca y D2x y D224 y D2O y D241 y D2， being composed of Cu y D22 O y D23 y D2 planes with two-leg ladders， has been performed。We discovered that heavily Ca-substituted compound （x=13.6） showed superconductivity under pressure （TイイD2cイエD2（onset）~ l2K at 3.5 Gpa）。为了进一步讨论超导电性，一个单一的水晶测量方法已经被制造出来了。超导电性在3.5 GPa和8 GPa之间观察（T-D2C-D2（一次性）至9 K，在4.5 GPa之间），由金属抵抗力在梯子之间结合。这一结果对压力的应用产生了一个关于交叉的强烈建议 ... 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 scManagement ing experiment for Sry D22.5 y D211.5 y D2Cu D22O y D241 y D2single cr #。梯子的自旋间隙能量被发现为32.1 meV，交换耦合被估计为90 meV （沿梯子）和65 meV （沿跑道）。特定热量、磁性可疑性和中子散射测量在Sry D214 x y D2Ca y D2 x y D2Cu y D2 O y D241 y D2单晶体上执行。The specific heat of Ca-substituted samples Sry D214 x y D2Ca y D224 y D241 y D2 showed a sharp phase transition at about 3 K。根据磁性可持续性的测量，它被确认为相位转换是从一个反磁性长范围顺序产生的。Besides， The Several Magnetic Bragg Peaks是由中子散射测量观测的，以及对链条和阶梯位置的一种可能的磁性结构。在这个系统中，单一状态和反磁秩序被环境压力下适当的空洞掺杂共存所定义。Less（低）

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