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arXiv 1901.03342cond-mat.mes-hall
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对称缺陷引起的4 $π$和8 $π$双约瑟夫森效应

4$π$ and 8$π$ dual Josephson effects induced by symmetry defects

Corneliu Malciu, Leonardo Mazza, Christophe Mora

摘要:

在拓扑绝缘体的边缘,塞曼场的方向和邻近的超导相之间的对偶性最近已被利用来预测磁约瑟夫森效应与4 $π$周期。我们重新审视后一种约瑟夫森效应,在这种双重性的光,并表明,相同的4 $π$量子异常发生时,桥接两个无自旋无自旋泵的p波超导区域,可以作为一个单一的和实验相关的超导量子点-一个点状缺陷小。这种作为双约瑟夫森效应的解释从来不需要存在马约拉纳模式,而是建立在具有Z拓扑不变量的绝热量子泵的拓扑性质上。它允许通过使用对称性不同于泵浦的对称性的点状缺陷(称为对称缺陷)来系统地构造任意周期性的双约瑟夫森效应,例如4 $π$和8 $π$。虽然绝热量子泵通常是通过映射到二维几何讨论,我们表明,这种现象没有任何对应的传统的二维系统。

英文摘要:

In topological insulator edges, the duality between the Zeeman field orientation and the proximitized superconducting phase has been recently exploited to predict a magneto-Josephson effect with a 4$π$ periodicity. We revisit this latter Josephson effect in the light of this duality and show that the same 4$π$ quantum anomaly occurs when bridging two spinless Thouless pumps to a p-wave superconducting region that could be as small as a single and experimentally-relevant superconducting quantum dot - a point-like defect. This interpretation as a dual Josephson effect never requires the presence of Majorana modes but rather builds on the topological properties of adiabatic quantum pumps with Z topological invariants. It allows for the systematic construction of dual Josephson effects of arbitrary periodicity, such as 4$π$ and 8$π$, by using point-like defects whose symmetry differs from that of the pump, dubbed symmetry defects. Although adiabatic quantum pumps are typically discussed via mappings to two-dimensional geometries, we show that this phenomenology does not have any counterpart in conventional two-dimensional systems.

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