量子微结构中的Josephson效应

文章为纪念Josephson效应发现50周年而作.文章介绍了当前关于几种量子微结构中Josephson效应的理论研究,涉及Josephson效应的基本物理现象和它在某些热点材料中的独特表现,如单层石墨纳米条带中的0-π转变,二维拓扑绝缘体中的手征性边态超导电流,以及半导体微腔中激子极化激元凝聚体之间的Josephson效应和直流-交流Josephson电流的转变.     

超导Josephson结直流I-V特性的数值计算

为了研究超导Josephson结的性质,选用四阶龙格-库塔法对RSJ模型下单个Josephson结及其阵列以及微波辐照下Josephson结的直流I-V特性进行了数值计算,并将模拟结果与实验结果进行了比较.     

Reveal the nematic topological superconductivity from the anisotropic unconventional Josephson effect: Theory and application to doped Bi_2Se_3

We propose a scheme to reveal the possible nematic superconducting order parameter in the doped Bi_2Se_3 by observing the anisotropic unconventional Josephson effect without an external magnetic field. We find the presence of an intrinsic π-phase in the spin-triplet channel of Andreev reflection. Its competition with the odd-parity superconducting gap phase can lead to unconventional Josephson effect in the Josephson junction, whose normal region is connected to the same side of the superconductor,called the U-shaped junction according to its geometry. For Josephson junctions with the interfaces perpendicular to the nematic direction, the competition will lead to a Josephson π-junctions. In the case where the interface is parallel to the nematic direction, it will lead to a Josephson 0-junction. Thus, this can directly reflect the nematic superconductivity. It is worth noting that Josephson coupling with the 4π period appears only in the normal injected channels. Interestingly, if the Josephson junction adopts a conventional geometry, it always exhibits a normal Josephson 0-junction regardless of the gap function taken by the doped Bi_2Se_3 and therefore cannot distinguish the pairing symmetry. We thus propose a superconducting quantum interference device containing a U-shaped Josephson junction to detect nematic superconductivity. This proposal not only can be applied to detect nematic superconductivity but also provides a feasible platform for topological quantum computation.     

全铌超导Josephson结的EWB仿真模型

通过超低温实验直接测量了制备的全铌Josephson结的电压源驱动RCSJ模型的I-V特性曲线。建立了Josephson结在电路仿真软件EWB中的模型,极大的方便了Josephson结及相关电路的仿真研究。利用这一新模型对Josephson结的基本特性进行了较为系统的研究,包括RSJ模型和RCSJ模型的直流驱动I-V特性曲线。     

超导弱连接中的Josephson电流在一个磁通量子内的振荡(Ⅰ) Josephson结

本文指出如果Josephson结处在Q值足够高的谐振腔内,当Josephson频率ω=2eV_0/h与谐振腔的本征频率ω_r发生谐振时,谐振的电磁场对Josephson结自身的反馈作用将导致超流电流在一个磁通量子内随磁场的小周期振荡。     

超导Josephson结直流Ⅰ-Ⅴ特性的数值计算

为了研究超导Josephson结的性质,选用四阶龙格-库塔法对RSJ模型下单个Josephson结及其阵列以及微波辐照下Josephson结的直流Ⅰ-Ⅴ特性进行了数值计算,并将模拟结果与实验结果进行了比较.     

直流和交流Josephson效应的研究

基于Feynman模型得到的Josephson方程,在求解过程中采取了ρ1=ρ2的假设,但这个假设在数学处理上并不严格。为了得到严格的结果,未进行上述假设,通过解微分方程得到了严格的Josephson方程,结果显示在一定条件下才能得到通常所说的Josephson方程。     

超导弱连接中的Josephson电流在一个磁通量子内的振荡(Ⅰ)——Josephson结

本文指出如果Josephson结处在Q值足够高的谐振腔内,当Josephson频率ω=(2eV₀)/h与谐振腔的本征频率ω_r发生谐振时,谐振的电磁场对Josephson结自身的反馈作用将导致超流电流在一个磁通量子内随磁场的小周期振荡。 关键词：     

超导Josephson结直流I—V特性的数值计算

为了研究超导Josephson结的性质，选用四阶龙格一库塔法对RSJ模型下单个Josephson结及其阵列以及微波辐照下Josephson结的直流I-V特性进行了数值计算，并将模拟结果与实验结果进行了比较．     

具有铁磁绝缘层的双层f波超导体结的直流Josephson电流

通过计算具有铁磁绝缘层的双层f波超导体结中铁磁绝缘层的磁散射对直流Josephson电流的影响,研究了f波超导体(fS)/铁磁绝缘层(FI)/f波超导体(fS)结的直流Josephson电流与温度和结两侧相位差((?))之间的关系.研究表明:fS/FI/fS结界面的粗糙散射和磁散射总是抑制结中准粒子的Andreev反射,降低流过fS/FI/fS结的直流Josephson电流,且结的直流Josephson电流随相位差的变化曲线强烈依赖于f波超导体的晶轴方位角(α).