By patterning mesoscopic crystals of Bi2Sr2CaCu2O8 (BSCCO) into electromagnetic resonators the oscillations of a large number of intrinsic Josephson junctions can be synchronized into a macroscopic coherent state accompanied by the emission of strong continuous wave THz-radiation. The temperature dependence of the emission is governed by the interplay of self-heating in the resonator and by re-trapping of intrinsic Josephson junctions which can yield a strongly nonmonotonic temperature dependence of the emission power. Furthermore, proper shaping of the resonators yields THzsources with voltage-tunable emission frequencies.
In this study, we investigated the terahertz radiation from a truncated edge square mesa structure made from a superconducting Bi_{2}Sr_{2}CaCu_{2}O_{8+δ} . Using a commercial software, the polarization characteristics were determined, and introduced, while accounting for the skin effect. The axial ratio was enhanced in the simulation by performing a parametric study on the design.
Optimal Condition for Strong Terahertz Radiation from Intrinsic Josephson Junctions
为了提高基于Bi $_2$ Sr $_2$ CaCu $_2$ O $_{8+δ}$单晶本征约瑟夫森结的太赫兹辐射功率，我们研究了嵌入电介质材料中的长圆柱形样品。通过调节介电常数，当辐射功率等于约瑟夫森等离子体引起的损耗时，辐射功率达到最大值。根据BSCCO单晶的性质，这产生了包裹材料的最佳介电常数。发现最大辐射功率与典型超导电流的平方和典型法向电阻的乘积或能隙能量的平方除以典型法向电阻成正比，为选择超导体作为强辐射源提供了依据。通过引入一个抗反射层，我们可以构建一个紧凑的设备与BSCCO圆柱和两个包装的介质层具有有限的厚度。
We demonstrate that parametric driving of suitable collective modes in cuprate superconductors results in a reflectivity $R>1$ for frequencies in the low terahertz regime. We propose to exploit this effect for the amplification of coherent terahertz radiation in a laser-like fashion. As an example, we consider the optical driving of Josephson plasma oscillations in a monolayer cuprate at a frequency that is blue-detuned from the Higgs frequency. Analogously, terahertz radiation can be amplified in a bilayer cuprate by driving a phonon resonance at a frequency slightly higher than the upper Jos…
Vortex-flow electromagnetic emission in stacked intrinsic Josephson junctions
通过观察Josephson涡旋流电流-电压特性中的多个子分支，证实了在Bi $_2$ Sr $_2$ CaCu $_2$ O $_{8+x}$的叠层本征约瑟夫森结中存在由约瑟夫森涡旋晶格运动激发的集体横向等离子体模.我们还观察到了约瑟夫森涡旋晶格与集体横等离子体模共振产生微波辐射的现象，这为研制约瑟夫森涡旋流电磁振荡器提供了可能。
Mutually synchronized macroscopic Josephson oscillations demonstrated by polarization analysis of superconducting terahertz emitters
University of Tsukuba（筑波大学）；Kyoto University（京都大学）；ENS, Université PSL, CNRS, Sorbonne Université, Université de Paris（巴黎高等师范学院，PSL大学，法国国家科学研究中心，索邦大学，巴黎大学）
We examine coupling interactions used to synchronize macroscopic Josephson oscillations induced in intrinsic Josephson junction (IJJ) mesa stacks made of a Bi2212 single crystal. Synchronized radiations of terahertz electromagnetic (EM) waves are detected under common voltage and current bias operations of two connected mesas with close individual radiation frequencies, while uncoupled and bimodal radiations are frequently observed in two mesas with different individual radiation frequencies. Detailed observations of the polarizations of the EM waves emitted when two mesas are biased in parall…
Collective Josephson Vortex Dynamics in Long Josephson Junction Stacks
我们研究了传统长约瑟夫森结（LJJ）堆和层状超导体中的集体相动力学，表现出本征LJJ行为。使用解释磁感应效应和局部电荷中性击穿的理论模型（即，电荷效应），我们发现在本征LJJ叠层如Bi $_2$ Sr $_2$ CaCu $_2$ O $_{8+y}$（BSCCO）中的Josephson涡旋的集体运动，包括Josephson等离子体模的色散和Swihart型速度，与常规LJJ叠层中的那些相比有显著的改变.在BSCCO中，充电效应$α$的强度小（即，$α\sim 0.1-0.4$），但它导致集体相动力学的显著变化，包括稳定性条件的变化。此外，我们表明，分裂的超导分支的电阻状态是由于集体运动的约瑟夫森涡旋。这些子分支在线性电流-电压状态下的扩展宽度取决于$α$，这表明了测量BSCCO中充电效应的另一种方法。
The phase dynamics of the stack of long Josephson junctions has been studied. Both inductive and capacitive couplings between Josephson junctions have been taken into account in the calculations. The IV--curve, bias current dependence of radiation power and dynamics of each JJs of the stack have been investigated. The coexistence of the charge traveling wave and fluxon states has been observed. This state can be considered as a new collective excitation in the system of coupled Josephson junctions. We demonstrate that the observed collective excitation leads to the decreasing of radiation powe…
Collective resonance modes of Josephson vortices in sandwiched stack of Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+x}$ intrinsic Josephson junctions
在长结极限下，观察到Bi $_{2}$ Sr $_{2}$ CaCu $_{2}$ O $_{8+x}$单晶的本征约瑟夫森结（IJJ）的电流-电压特性中，低偏置涡旋流分支在密集约瑟夫森涡旋态分裂成多个子分支.每个子分支对应于串联耦合的约瑟夫森结中的等离子体模式。分裂成低偏置线性子分支的斜率和子分支间模式切换字符的扩展是在良好的定量协议与预测的弱，但有限的结间电容耦合模型与电感耦合。这表明电容耦合在精确描述串联堆叠IJJ中的涡旋动力学中的作用的重要性。
We have theoretically demonstrated the emission of circularly-polarized terahertz (THz) waves from intrinsic Josephson junctions (IJJs) which is locally heated by an external heat source such as the laser irradiation. We focus on a mesa-structured IJJ whose geometry is slightly deviate from a square and find that the local heating make it possible to emit circularly-polarized THz waves. In this mesa, the inhomogeneity of critical current density induced by the local heating excites the electromagnetic cavity modes TM (1,0) and TM (0,1), whose polarizations are orthogonal to each other. The mix…
Two parallel stacks of coupled Josephson junctions are investigated to clarify the physics of transitions between the rotating and oscillating states and their effect on the IV-characteristics of the system. The detailed study of phase dynamics and bias dependence of the superconducting and diffusion currents allows one to explain all features of simulated IV-characteristics and demonstrate the correspondence in their behavior. The coupling between JJ in the stacks leads to the branching of IV-characteristics and a decrease in the hysteretic region. The crucial role of the diffusion current in…
Broadly Tunable Sub-terahertz Emission from Internal Branches of the Current-voltage Characteristics of Superconducting Bi2Sr2CaCu2O8+d Single Crystals
Japan Society for the Promotion of Science（日本学术振兴会）；Quantum Beam Science Directorate, Japan Atomic Energy Agency（日本原子力机构量子束科学部）；Graduate School of Pure & Applied Sciences, University of Tsukuba（筑波大学纯科学与应用科学学院）
Scaling behavior of the crossover to short-stack regimes of Josephson vortex lattices in Bi$_2$Sr$_2$CaCu$_2$O$_{8+δ}$ stacks
本文系统地研究了具有不同几何形状和超导各向异性参数的Bi $_2$ Sr $_2$ CaCu $_2$ O $_{8+δ}$微制造结中约瑟夫森涡旋（JV）流阻的振荡。当平行于$ab$平面的外加磁场增加时，具有对应于$ϕ_0/2$ par原子约瑟夫森结的周期的振荡变为具有双倍周期的振荡。该交叉由结长度和各向异性参数两者缩放，表明有利于三角形JV晶格的体电感耦合被替换为JV晶格的占主导地位的相互作用的表面变形能。这些结果表明，在较小且各向异性更强的样品中，在较高的磁场下，同相正方形JV晶格明显。
The peculiarities of the phase dynamics of stacks of coupled Josephson junctions with topologically trivial and nontrivial barriers have been investigated numerically and their comparative analysis is carried out. The effect of coupling and dissipation parameters on the parametric resonance in the breakpoint region is shown. It is found that the dependence of the breakpoint voltage on the dissipation parameter demonstrates a minimum due to the changing of frequency of longitudinal plasma wave. We have shown that in case of the stack with nontrivial barriers the observed minimum shifts along th…
Enhanced Macroscopic Quantum Tunneling in Bi$_2$Sr$_2$CaCu$_2$O$_{8+δ}$ Intrinsic Josephson Junction Stacks
我们用微波辐射研究了Bi $_2$ Sr $_2$ CaCu $_2$ O $_{8+δ}$本征约瑟夫森结在毫开尔文温度下的宏观量子隧穿.测量结果表明，均匀切换N结堆的逃逸率是约$N^2$倍高于具有相同的等离子体频率的单个结。我们认为，这种巨大的增强堆栈中的宏观量子隧穿率是由电流的波动，发生在由环境的阻抗加载的结的串联阵列。
Microwave distribution in stacked Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+x}$ intrinsic Josephson junctions in a transmission-line geometry
研究了矩形叠层（15 $μ$ m $\times$ 0.72 $μ$ m $\times$ 60 nm）$_{2}$ $_{2}$ $_{2}$ O $_{8+x}$本征约瑟夫森结（IJs）内的微波分布。该堆叠被微制造成传输线几何形状，其中几百nm厚的Au层沉积在堆叠的顶部和底部。通过测量不同微波功率下W波段IJs隧穿临界电流的异常抑制来监测微波分布。这种技术可以提供有价值的信息的微波传输模式内的夹层堆叠的IJs，这是非常重要的高频器件应用，使用IJs，如磁通流太赫兹振荡器。
