Interference effects in isolated Josephson junction arrays with geometric symmetries
Interference effects in isolated Josephson junction arrays with geometric symmetries
复制标题
具有几何对称性的孤立约瑟夫森结阵列的干扰效应
DOI：
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发表时间：
2001
期刊：
影响因子：
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通讯作者：
G. Blatter
中科院分区：
文献类型：
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作者：
D. Ivanov;L. Ioffe;V. Geshkenbein;G. Blatter
减小Josephson结阵列中结的大小将系统从经典状态带入量子状态，并将岛屿上的凝聚相转变为周期量子变量。在适当的条件下，这种量子阵列表现出阿哈罗诺夫-博姆-卡舍尔型干涉效应，通过向阵列中添加一个库珀对来改变宏观物体的光谱。我们讨论了一个由N个相同结组成的孤立对称环绕着半个超导磁通量量子的情况。我们认为，如果阵列上的库珀对总数能被N整除，则基态是非简并的，否则（在杂散电荷被栅极电压补偿后）基态是双简并的。这一结果首先建立在支配约瑟夫森和充电能的两个相反的极限上，并进一步用对称参数解释。只要保持基态对称性，它的简并度在整个充电-约瑟夫森能量比范围内保持不变。这种干涉效应可能与量子计算超导结阵列的应用有关。
Reducing the size of the junctions in a Josephson junction array takes the system from the classical to the quantum regime and turns the condensate phases on the islands into periodic quantum variables. Under suitable conditions such quantum arrays exhibit Aharonov-Bohm-Casher-type interference effects which change the spectrum of this macroscopic object by the addition of one Cooper pair to the array. We discuss the case of an isolated symmetric loop of N identical junctions encircling one half superconducting quantum of magnetic flux. We argue that the ground state is nondegenerate if the total number of Cooper pairs on the array is divisible by N, and doubly degenerate otherwise (after the stray charges are compensated by the gate voltages). This result is first established in the two opposite limits of dominating Josephson and charging energies, and is further explained using symmetry arguments. As long as the ground-state symmetry is preserved, its degeneracy remains unchanged in the entire range of charging-to-Josephson energy ratio. Such interference effects may be relevant in applications of superconducting junction arrays for quantum computing.