The study on the superconductive properties of the Pr-based cuprates with quasi-one-dimensional CuO double chains

本研究的目的是阐明具有准一维CuO双链的Pr_2Ba_4Cu_7O_<15-δ> (Pr247)氧化物超导体的超导性能。因此，本研究的另一个目的是利用改进的Bridgman砧法研制10 gpa级高压电池。成功地合成了Pr247氧化物，经过还原处理后，Pr247氧化物表现出T_c= 15 K的超导性（SC），尽管存在“pr问题”。Pr247的还原处理通过控制CuO单链的缺氧量引起载流子密度的变化。T_c取决于真空退火过程中重量变化估计的氧缺乏δ。这表明，与空穴基氧化物超导体不同，Pr247中的SC是由于氧损失（即电子掺杂）而出现的。此外，NQR实验表明，在CuO双链上，SC是在…基于Tomonaga-Luttinger液体理论研究了一维导电机理。Pr247上的CuO双链可以看作是一维结构，其结果很好地解释了Pr247上的实验结果。在10gpa压力下，研究了压力对Pr247 SC的影响。高压是由本工作研制的一种新改良的Bridgman顶砧式压力池产生的。在直径φ 1.5 mm的扩样空间内，可产生高达10 GPa的高压，并可同时测量两个样品的电阻率。通过电阻率变化检测Bi、Te和Sn的结构转变压力来校准压力。低温下的校准是通过对Pb超导温度的压力效应的交流磁化率测量得出的。这些校准数据表明，即使在低于10 K的低温下，夹紧的电池也能在室温下保持压力。用Bridgman砧型电芯测量了δ = 0.26、0.68和0.79的Pr_2Ba_4Cu_7O_<15δ>在压力下的电阻率。研究结果综述如下：(1)高压抑制Pr247上的SC。(2)随着6的增大，抑制SC所需的压力也随之增大。(3) SC消失后，增加的压力引入了低温下类似半导体的电阻率行为。少

The purpose of the present study is to clarify the superconductive properties of the Pr_2Ba_4Cu_7O_<15-δ> (Pr247) oxide superconductor with the quasi-one-dimensional CuO double chains. A high pressure apparatus is very important for this research, Therefore, another purpose of this study is do develop the 10 GPa-class high pressure cell by means of a modified Bridgman anvil method.A Pr247 oxide have been synthesized successfully, and showed superconductivity (SC) with T_c= 15 K after reduction treatment, in spite of the "Pr-issue". Reduction treatment on Pr247 caused the carrier density change by controlling the amount of oxygen deficiency in the CuO single chains. The T_c depends on the oxygen deficiency δ which is estimated from the weight change during the vacuum annealing. This indicates that the SC in the Pr247 emerges as a result of oxygen loss, i.e., electron doping, unlike in hole-based oxide superconductors. Additionally, the NQR experiment revealed that the SC is realized at … More the CuO double chains. We studied the one-dimensional conduction mechanism based on Tomonaga-Luttinger liquid theory. The CuO double chain on Pr247 can be treated as a one-dimensional (ID) structure and their results explained well the experimental results on Pr247.The pressure effects on the SC of the Pr247 have been investigated up to 10 GPa. The high pressure was produced by a newly modified Bridgman anvil type pressure cell which has been developed in the present work. The new pressure cell can produce high pressure up to 10 GPa with the expanded sample space with i.d. φ 1.5 mm, in which the resistivity for two samples can be measured at the same time. The pressure was calibrated by the structural transformation pressure of Bi, Te and Sn detected by resistivity change. The calibration at low temperature was derived from the AC susceptibility measurements on the pressure effects on the superconducting temperature of Pb. These calibration data suggested that the clamped cell holds a pressure at room temperature even in the low temperature below 10 K. The electrical resistivity on the Pr_2Ba_4Cu_7O_<15δ> with δ = 0.26, 0.68 and 0.79 was measured under the pressure with the Bridgman anvil type cell. The results are reviewed as follows;(1) High pressure suppresses the SC on the Pr247.(2) With increasing 6, the pressure required to suppress the SC is also increased.(3) After the SC vanished, the increased pressure introduces the semiconductor-like behavior of the resistivity at low temperature. Less