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自从YBa_2Cu_3O_7(YBCO)高温超导体发现以来,其微波表面电阻一直是大家关注的问题之一.人们发现:尽管C取向YBCO薄膜的微波表面电阻比金属Cu低一个数量级以上,但仍远大于BCS理论的预测值,而且表面电阻与温度的依赖关系与理论预测也偏差较大.这些不一致性到底是高温超导材料的内禀性质,还是材料本身不完整性的体现,目前还难以定论.一般认为,表面电阻由两部分组成:一部分由材料的本征损耗引起的,另一部分则由材料的非本征损耗引起的.由于高温超导体的本征损耗还无法确定,所以,为了了解其本征损耗,唯一可行的途径就是首先来确定所有的非本征损耗.我们认为,YBCO高温超导薄膜的
The microwave surface resistance has been one of the concerns since the discovery of the YBCO high temperature superconductor.It was found that although the microwave surface resistance of the C-oriented YBCO film is more than one order of magnitude lower than that of Cu, it is still much larger than that of the BCS theory Prediction value, and the dependence of surface resistance on temperature is also deviated from the theoretical prediction.This inconsistency in the end is the intrinsic nature of high-temperature superconducting materials, or the material itself is not the embodiment of integrity, it is difficult to determine .It is generally believed that, The surface resistance consists of two parts: one is caused by the intrinsic loss of the material and the other is caused by the extrinsic loss of the material. Since the intrinsic loss of a high-temperature superconductor can not be determined, in order to know its intrinsic loss, The only viable route is to determine all extrinsic losses first. We believe that the YBCO high temperature superconducting thin film