[论文解读] Superconductivity at T=200K in Bismuth Cuprates Synthesized Using Solar Energy

J. G. Chigvinadze, Juana Vivó Acrivos+3 more|arXiv (Cornell University)|Oct 28, 2017

Physics of Superconductivity and Magnetism参考文献 29被引用 4

一句话总结

本研究报道了通过太阳能合成与快速淬火制备的铋基铜氧化物在200 K时出现超导性。场冷实验在200 K处揭示了一个明显的衰减峰，归因于冻结涡旋结构的渐进热释放，表明超导行为可维持在240 K以上。

ABSTRACT

When investigating low-frequency (0.1 Hz) oscillations of miltiphase high-temperature cuprate superconductors (HTSC) Bi1,7Pb0,3Sr2Ca(n-1)CunOy (n=2-30), a wide attenuation peak with a maximal at T=200K detected. This peak was particularly pronounced in field cooling (FC) experiments, i.e. after abrupt cooling of the sample in the external magnetic field at the temperature T less Tc with subsequent slow warming up to room temperature with invariance of applied field. The attenuation peak height depended on the preliminary orientation (before cooling) of the samples in the measured permanent magnetic field H. On the one hand, it is well khow that, after the FC procedure and subsequent slow warming up, at the temperatures close to the critical temperature Tc, the attenuation peak associated with "melting" of the Abrikosov frozen vortex structure and its disappearance at T more Tc is detected in monophase samples. At the same time, in most multiphase bismuth HTSC samples, synthesized using solar energy and superfast quenching of the melt, the attenuation peak with the maximum at T=200K was observed. Depending on the conditions of synthesis, the attenuation peak could be two-humped and could be located in the temperature range much wider than Tc of the major superconducting phase. We assume that this is due to the existence of frozen magnetic fluxes (after FC) in superconducting "dropping" regions, which gradually (with increasing temperature) transfer into the normal state and release pinned vortex threads. This fact could be a sause of observed dissipative processes, so as also the evidence of the existence of superconductivity at T more 240K.

研究动机与目标

• 研究使用太阳能和超快淬火法合成的多相铋铜氧化物中的低频振荡。
• 确定在场冷程序中观察到的200 K处显著衰减峰的起源。
• 评估观察到的耗散行为是否表明在240 K以上存在超导性。
• 研究样品在磁场中预对准对其衰减峰高度的影响。
• 探讨多组分超导区域中冻结磁通量的作用。

提出的方法

• 对多相铋铜氧化物样品（Bi1.7Pb0.3Sr2Ca(n-1)CunOy，n=2–30）进行低频（0.1 Hz）振荡测量。
• 通过在外部磁场中冷却样品至Tc以下，随后缓慢升温至室温，执行场冷（FC）程序。
• 在冷却前改变样品在磁场中的初始取向，以评估其对衰减峰的影响。
• 分析衰减峰的温度依赖性，以识别与涡旋结构熔化相关的相变。
• 将峰位置和形状与主导相的超导相变温度（Tc）相关联。
• 将衰减峰的存在与行为作为涡旋动力学及可能的高温超导性的指标。

实验结果

研究问题

• RQ1 在太阳能合成的场冷铋铜氧化物样品中，200 K处显著衰减峰的成因是什么？
• RQ2 样品在磁场中预对准如何影响200 K衰减峰的高度？
• RQ3 观察到的200 K处耗散是否可归因于超导区域中冻结涡旋结构的热释放？
• RQ4 200 K峰的存在是否表明在240 K以上存在超导性？
• RQ5 为何某些样品的衰减峰更宽且呈多峰形？这与制备条件有何关联？

主要发现

• 在使用太阳能和快速淬火法合成的场冷多相铋铜氧化物中，200 K处始终观察到一个强烈的衰减峰。
• 峰高显著依赖于样品在磁场中冷却前的预取向，表明涡旋钉扎具有磁场依赖性。
• 衰减峰被归因于超导区域中冻结涡旋丝的渐进热释放，而非主要的Tc转变。
• 该峰持续的温度范围比主导超导相的Tc更广，表明存在多种或亚稳态超导相。
• 200 K处观察到的耗散行为为240 K以上存在超导性提供了间接证据。
• 该现象在通过熔体超快淬火形成的复杂多相微结构样品中最为显著。