Intrinsic Josephson Junctions and their Terahertz Functions

高温超导杯状氧化物（HTSC）具有由CuO_2超导层和中间的绝缘层或正常导电层组成的层状晶体结构，表现出很强的各向异性。特别是，跨层的电流传输行为由约瑟夫森弱耦合控制，并被称为本征约瑟夫森效应。利用本征约瑟夫森效应由高温超导单晶制成的结器件称为本征约瑟夫森结（IJJ）。IJJ是唯一一种可以利用HTSC的大能隙特性的HTSC约瑟夫森器件，并且有望成为在高达太赫兹的非常高的频率下工作的有用器件。本研究计划旨在揭示IJJ的高频特性，以开发用于太赫兹波检测和振荡的超导固态器件。我们研究了（1）结特性的精确控制和（2）外加电磁波对结的影响。 ...更多信息 对于（1），我们发展了一种通过注入强氧亲合性杂质来控制结特性的新方法，对于（2），我们成功地观察到了由小型制冷机和永磁体组成的磁通流实验系统产生的涡流状态的高频响应。利用这个系统，我们发现了一个显著的过零阶跃，表明运动的约瑟夫森涡旋对外加电磁波的锁相。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或反之亦然，并适用于通过使用IJJ的太赫兹波的放大和振荡。此外，我们还发现沿涡旋运动方向沿着在IJJ中引入周期性势能有效地发展IJJ上Josephson涡旋的同相相干运动，这是实现IJJ有效发射电磁波的关键。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