Vigliotti Lucia, Calzona Alessio, Traverso Ziani Niccolò, Bergeret F Sebastian, Sassetti Maura, Trauzettel Björn
Dipartimento di Fisica, Università degli Studi di Genova, Via Dodecaneso 33, 16146 Genova, Italy.
Institute for Theoretical Physics and Astrophysics, University of Würzburg, D-97074 Würzburg, Germany.
Nanomaterials (Basel). 2023 Jan 31;13(3):569. doi: 10.3390/nano13030569.
Josephson junctions (JJs) in the presence of a magnetic field exhibit qualitatively different interference patterns depending on the spatial distribution of the supercurrent through the junction. In JJs based on two-dimensional topological insulators (2DTIs), the electrons/holes forming a Cooper pair (CP) can either propagate along the same edge or be split into the two edges. The former leads to a SQUID-like interference pattern, with the superconducting flux quantum ϕ0 (where ϕ0=h/2e) as a fundamental period. If CPs' splitting is additionally included, the resultant periodicity doubles. Since the edge states are typically considered to be strongly localized, the critical current does not decay as a function of the magnetic field. The present paper goes beyond this approach and inspects a topological JJ in the tunneling regime featuring extended edge states. It is here considered the possibility that the two electrons of a CP propagate and explore the junction independently over length scales comparable to the superconducting coherence length. As a consequence of the spatial extension, a decaying pattern with different possible periods is obtained. In particular, it is shown that, if crossed Andreev reflections (CARs) are dominant and the edge states overlap, the resulting interference pattern features oscillations whose periodicity approaches 2ϕ0.
在存在磁场的情况下，约瑟夫森结（JJs）会根据通过结的超电流的空间分布呈现出性质不同的干涉图样。在基于二维拓扑绝缘体（2DTIs）的约瑟夫森结中，形成库珀对（CP）的电子/空穴既可以沿着同一条边缘传播，也可以被分裂到两条边缘上。前者会导致类似超导量子干涉器件（SQUID）的干涉图样，以超导磁通量子ϕ0（其中ϕ0 = h/2e）作为基本周期。如果额外考虑库珀对的分裂，那么所得的周期性会翻倍。由于边缘态通常被认为是强局域化的，临界电流不会随磁场而衰减。本文超越了这种方法，研究了处于隧穿区域且具有扩展边缘态的拓扑约瑟夫森结。这里考虑了库珀对的两个电子在与超导相干长度相当的长度尺度上独立传播并探索结的可能性。由于空间扩展，会得到具有不同可能周期的衰减图样。特别地，研究表明，如果交叉安德烈夫反射（CARs）占主导且边缘态重叠，那么所得的干涉图样会呈现出周期性接近2ϕ0的振荡。
