论文标题
作为约瑟夫森二极管的不对称高谐波鱿鱼
Asymmetric higher-harmonic SQUID as a Josephson diode
论文作者
论文摘要
我们从理论上研究了两个约瑟夫森连接中具有不同流相关关系的不对称的两结鱿鱼，涉及较高的约瑟夫森谐波。我们的主要重点是具有正弦电流相关的鱿鱼环中的一个连接处的“最小模型”，另一个具有额外的第二次谐波。当前的电压特性（CVC）被证明是不对称的，$ i（-v）\ neq -i（v）$。不对称是由于第二个谐波的存在，并取决于通过干涉仪回路的磁通量，仅在通量的特殊值（例如整数或半成位）中消失。因此，该系统证明了可容纳通量的Josephson二极管效应（JDE），其最简单的表现是临界电流的方向依赖性。我们分析了整体$ i（v）$形状的不对称性，无论是在没有外部AC辐射的情况下。在外部信号的电压源情况下，CVC证明了夏皮罗尖峰。整数尖峰是不对称的（JDE的表现），而半级尖峰仍然是对称的。在当前源情况下，CVC演示了Shapiro步骤。 JDE以整体CVC形状的不对称性表现出来，包括整数和半数步骤。
We theoretically investigate asymmetric two-junction SQUIDs with different current-phase relations in the two Josephson junctions, involving higher Josephson harmonics. Our main focus is on the "minimal model" with one junction in the SQUID loop possessing the sinusoidal current-phase relation and the other one featuring additional second harmonic. The current-voltage characteristic (CVC) turns out to be asymmetric, $I(-V) \neq -I(V)$. The asymmetry is due to the presence of the second harmonic and depends on the magnetic flux through the interferometer loop, vanishing only at special values of the flux such as integer or half-integer in the units of the flux quantum. The system thus demonstrates the flux-tunable Josephson diode effect (JDE), the simplest manifestations of which is the direction dependence of the critical current. We analyze asymmetry of the overall $I(V)$ shape both in the absence and in the presence of external ac irradiation. In the voltage-source case of external signal, the CVC demonstrates the Shapiro spikes. The integer spikes are asymmetric (manifestation of the JDE) while the half-integer spikes remain symmetric. In the current-source case, the CVC demonstrates the Shapiro steps. The JDE manifests itself in asymmetry of the overall CVC shape, including integer and half-integer steps.
