Intrinsic Josephson Junctions and their Terahertz Functions

高温超导杯氧化物(HTSC)由于其由超导CuO_2层和其间的绝缘层或正常导电层组成的层状晶体结构而表现出强烈的各向异性。具体地说，电流输运行为受约瑟夫森弱耦合的支配，被称为本征约瑟夫森效应。利用本征约瑟夫森效应制作的高温超导单晶结器件是本征约瑟夫森结(IJJ)。IJJ是唯一可以利用高温超导的大能隙特性的高温超导约瑟夫森器件，有望成为在极高频率下运行的有用器件，最高可达太赫兹制度。本研究项目旨在揭示IJJ的高频特性，以开发用于太赫兹波探测和振荡的超导固态器件。研究了(1)结性质的精确控制和(2)外加电磁波对TH-…的影响对于IJJ中约瑟夫森涡旋的更多集体运动，我们发展了一种新的方法来控制结的性质。对于(1)，我们发展了一种新的方法来控制结的性质。对于(2)，我们成功地观测到了由紧凑的低温制冷器和永久磁体组成的磁通流动实验系统产生的涡流状态的高频响应。利用该系统，我们发现了一个显著的过零步，这表明运动的约瑟夫森涡旋对外加的电磁波是锁相的。这一结果是非常重要的，因为很明显电磁波驱动约瑟夫森涡旋，反之亦然，适用于IJJ对太赫兹波的放大和振荡。此外，我们还发现沿涡旋运动方向在IJJ中引入的周期势有效地促进了IJJ上方约瑟夫森涡旋的同相相干运动，这是实现IJJ有效发射电磁波的关键。较少

High-Tc superconducting cup per oxides (HTSC) show strong anisotropies due to their layered crystal structures consisting of the superconducting CuO_2 layers and the insulating or normal conducting layers in between them. In particular, current transport behaviors across the layers are governed by Josephson weak coupling and are termed the intrinsic Josephson effects. Junction devices fabricated of the HTSC single crystals to use the intrinsic Josephson effects are the intrinsic Josephson junctions (IJJ). The IJJ is the only HTSC Josephson device which can exploit the large energy gaps characteristic of the HTSC and expected to be useful devices operating at very high frequencies up to the terahertz regime. This research project aims to reveals high frequency properties of IJJ to develop superconducting solid state devices for detection and oscillation of terahertz waves. We study (1)precise control of junction properties and (2)effects of externally applied electromagnetic waves on th … More e collective motion of Josephson vortices in the IJJ.For (1), we develop a novel method to control the junction properties by the ion implantation of impurities with strong oxygen affinities.For(2), we succeeded to observe high frequency responses on the vortex flow state which is generated by a flux-flow experiment system designed for this research consisting of a compact cryo-cooler and permanent magnets. By using this system, we found a remarkable zero-crossing step that indicates phase-locking of moving Josephson vortices to the externally applied electromagnetic waves. This results is quite important because it is evident that the electromagnetic waves drives Josephson vortices or vice versa and applicable to amplification and oscillation of terahertz waves by using IJJ. Furthermore, we found periodic potentials introduced in the IJJ along the direction of vortex motion is effective to develop the in-phase coherent motion of the Josephson vortices over the IJJ that is a key point to realize the efficient emission of electromagnetic waves from the IJJ. Less