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arXiv 2006.08489cond-mat.supr-con
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外部hydrostatic pressure作用下Sr0.5RE 0.5FBiS 2(RE:La,Ce,Pr,Nd,Sm)中两个体超导相的演化

Evolution of two bulk-superconducting phases in Sr0.5RE0.5FBiS2 (RE: La, Ce, Pr, Nd, Sm) by external hydrostatic pressure effect

Aichi Yamashita, Rajveer Jha, Yosuke Goto, Akira Miura, Chikako Moriyoshi, Yoshihiro Kuroiwa, Chizuru Kawashima, Kouhei Ishida, Hiroki Takahashi, Yoshikazu Mizuguchi

摘要:

采用固相反应法合成了Sr 1-xRExFBiS 2(RE:La,Ce,Pr,Nd,Sm)多晶样品,并用同步辐射X射线衍射仪对其进行了表征。虽然所有的Sr0.5RE0.5FBiS2样品在环境压力下的转变温度(Tc)在2.1-2.7 K的范围内表现出超导性,估计的超导体积分数是小的。这表明在环境压力下这些样品中的超导性的非体性质。一个戏剧性的演变体超导相实现了施加外部流体静压。在低于1GPa的压力附近,诱导体超导性,其Tc为2.5- 2.8K,这被称为低P相。此外,高P相(Tc = 10.0-10.8 K)具有体积特性,在较高的压力下观察到。压力-Tc相图表明,出现高磷相的临界压力随掺杂稀土离子半径的减小而增大。根据高压X射线衍射测量的Sr0.5La0.5FBiS2,结构相变从四斜晶系到单斜晶系也发生在约1.1 GPa。因此,该相变表示类似于LaO 0.5F 0.5BiS 2中的转变的压力诱导超导-超导转变。在Sr 0.5RE 0.5FBiS2中由外部流体静压效应引起的体超导相有望用于评估BiCh 2基超导体的超导电性机制。

英文摘要:

Polycrystalline samples of Sr1-xRExFBiS2 (RE: La, Ce, Pr, Nd, and Sm) were synthesized via the solid-state reaction and characterized using synchrotron X-ray diffraction. Although all the Sr0.5RE0.5FBiS2 samples exhibited superconductivity at transition temperatures (Tc) within the range of 2.1-2.7 K under ambient pressure, the estimated superconducting volume fraction was small. This indicated the non-bulk nature of superconductivity in these samples under ambient pressure. A dramatic evolution of the bulk superconducting phases was achieved on applying an external hydrostatic pressure. Near pressures below 1 GPa, bulk superconductivity was induced with a Tc of 2.5-2.8 K, which is termed as the low-P phase. Moreover, the high-P phase (Tc = 10.0-10.8 K) featuring bulk characteristics was observed at higher pressures. Pressure-Tc phase diagrams indicated that the critical pressure for the emergence of the high-P phase tends to increase with decreasing ionic radius of the doped RE ions. According to the high-pressure X-ray diffraction measurements of Sr0.5La0.5FBiS2, a structural phase transition from tetragonal to monoclinic also occurred at approximately 1.1 GPa. Thus, this phase transition indicates a pressure-induced superconducting-superconducting transition similar to the transition in LaO0.5F0.5BiS2. Bulk superconducting phases in Sr0.5RE0.5FBiS2 induced by the external hydrostatic pressure effect are expected to be useful for evaluating the mechanisms of superconductivity in BiCh2-based superconductors.

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