Intrinsic Josephson effects in layered superconductors
Intrinsic Josephson effects in layered superconductors
复制标题
层状超导体的本征约瑟夫森效应
DOI：
10.1007/bfb0107518
复制
发表时间：
1997
影响因子：
1.7
通讯作者：
P. Müller
中科院分区：
文献类型：
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作者：
P. Müller
高Tc超导体的大的各向异性和极短的相干长度表明，层状晶体结构映射到超导序参量的周期调制。即使是理想的单晶体也应该由一系列超导层和非超导层堆叠而成。三维相位相干性由层之间的约瑟夫森电流提供。由于典型的层间距离约为15 μ m，因此3 μm厚的单晶应该表现为2000个约瑟夫森结的堆叠。这一假设通过测量Bi 2Sr 2CaCu 2 O 8、（Bi 1 −yPby）2Sr 2CaCu 2 O 8、Tl 2Ba 2Ca 2Cu 3 O 10和Pr 2 − xCexCuO 4单晶的直流和交流约瑟夫森效应得到了详细的证明。在3.5和95 GHz之间的频率的微波发射实验揭示明确的样品中的结的数量。该数字由晶体厚度除以15 Å给出，即每对CuO 2双层形成约瑟夫森结。最近在有机超导体κ-（BEDT-TTF）2Cu的单晶上获得了类似的结果，包括微波发射。（NCS）2。这一观察结果支持了这样的结论：在任何具有足够高的各向异性的层状超导体中，超导序参量是空间不均匀的先验。在原子尺度上对超导性的调制开辟了一个新的应用：晶体本身就是超导器件，不需要人工处理。这些器件的基本单元是一个晶胞，其Ginzburg-Landau相干长度的尺寸平行于层和层间距离，即一个只有150个原子的立方体，其尺寸为15·15·153。
The large anisotropy and the extremely short coherence lengths of the high-Tcsuperconductors suggest that the layered crystal structure is mapped onto a periodic modulation of the superconducting order parameter. Even an ideal single crystal should consist of a stacked series of superconducting and non-superconducting layers. Three-dimensional phase coherence is provided by Josephson currents between the layers. As the typical interlayer distance is approximately 15 Å, a single crystal of 3 μm thickness should behave like a stack of 2000 Josephson junctions. This hypothesis is proved in every detail by measurements of the DC as well as the AC Josephson effects on single crystals of Bi2Sr2CaCu2O8, (Bi1−yPby)2Sr2CaCu2O8, Tl2Ba2Ca2Cu3O10and Pr2−xCexCuO4. Microwave emission experiments at frequencies between 3.5 and 95 GHz reveal explicitly the number of junctions in the samples. This number is given by the crystal thickness divided by 15 Å, i.e. every pair of CuO2bilayers forms a Josephson junction.Similar results, including microwave emission, have been obtained very recently on single crystals of the organic superconductor κ-(BEDT-TTF)2Cu(NCS)2. This observation supports the conclusion that in any layered superconductor with sufficiently high anisotropy the superconducting order parameter is spatially inhomogeneous a priori.The modulation of superconductivity on an atomic scale opens up a new application: the crystals by themselves are superconducting devices without the need of artificial treatments. The basic unit of those devices is a cell with the dimensions of the Ginzburg-Landau coherence length parallel to the layers and the interlayer distance i.e. a cube with 15·15·153which contains only 150 atoms.
N.TAKEZAWA：“层状超导体中上临界场的角度依赖性”Physica C.
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