Frombach Daniel, Recher Patrik
Institut für Mathematische Physik, Technische Universität Braunschweig, D-38106 Braunschweig, Germany.
Laboratory for Emerging Nanometrology Braunschweig, D-38106 Braunschweig, Germany.
J Phys Condens Matter. 2022 Feb 23;34(16). doi: 10.1088/1361-648X/ac4dbc.
Topological Josephson junctions (TJJs) have been a subject of widespread interest due to their hosting of Majorana zero modes. In long junctions, i.e. junctions where the junction length exceeds the superconducting coherence length, TJJs manifest themselves in specific features of the critical current (Beenakker 2013017003). Here we propose to couple the helical edge states mediating the TJJ to additional channels or quantum dots, by which the effective junction length can be increased by tunable parameters associated with these couplings, so that such measurements become possible even in short junctions. Besides effective low-energy models that we treat analytically, we investigate realizations by a Kane-Mele model with edge passivation and treat them numerically via tight binding models. In each case, we explicitly calculate the critical current using the Andreev bound state spectrum and show that it differs in effectively long junctions in the cases of strong and weak parity changing perturbations (quasiparticle poisoning).
拓扑约瑟夫森结（TJJs）由于其承载马约拉纳零模而受到广泛关注。在长结中，即结长度超过超导相干长度的结中，TJJs在临界电流的特定特征中表现出来（Beenakker 2013017003）。在这里，我们提议将介导TJJ的螺旋边缘态与额外的通道或量子点耦合，通过与这些耦合相关的可调参数可以增加有效结长度，从而即使在短结中也能进行此类测量。除了我们进行解析处理的有效低能模型外，我们还研究了具有边缘钝化的凯恩 - 梅勒模型的实现，并通过紧束缚模型对其进行数值处理。在每种情况下，我们使用安德列夫束缚态谱明确计算临界电流，并表明在强和弱宇称变化扰动（准粒子中毒）的情况下，有效长结中的临界电流是不同的。
