标题： 量子点通过浮置超导岛耦合的马约拉纳模式 显示英文标题

标题： Majorana modes in quantum dots coupled via a floating superconducting island

摘要： 马约拉纳模式可以在量子点（QDs）通过接地超导体耦合的阵列中设计，从而有效地实现人工基特夫链。 由两个QDs组成的最小基特夫链可以在参数空间中的离散点上容纳完全局域化的马约拉纳模式，这些点被称为马约拉纳甜点。 在此，我们通过理论研究一个由两个QDs通过浮动超导岛耦合的设置来扩展之前的工作。 我们研究了岛的电荷能的影响以及由此产生的最小基特夫链的特性。 我们最初采用一个最小微扰模型，在QD-岛耦合较弱的区域有效，以推导出马约拉纳甜点和基态简并度的分裂作为可调物理参数的函数的解析表达式。 然后使用一个显式描述岛内部自由度的微观模型来验证这种微扰近似的结果。 我们的工作表明，即使岛没有被调节到电荷简并点，马约拉纳甜点仍然存在。 与接地超导体中的基特夫链不同，这些甜点涉及具有明确粒子数的状态之间的简并。 显示英文摘要

摘要： Majorana modes can be engineered in arrays where quantum dots (QDs) are coupled via grounded superconductors, effectively realizing an artificial Kitaev chain. Minimal Kitaev chains, composed by two QDs, can host fully-localized Majorana modes at discrete points in parameter space, known as Majorana sweet spots. Here, we extend previous works by theoretically investigating a setup with two QDs coupled via a floating superconducting island. We study the effects of the charging energy of the island and the properties of the resulting minimal Kitaev chain. We initially employ a minimal perturbative model, valid in the weak QD-island coupling regime, to derive analytic expressions for the Majorana sweet spots and the splitting of the ground state degeneracy as a function of tunable physical parameters. The conclusions from this perturbative approximation are then benchmarked using a microscopic model that explicitly describes the internal degrees of freedom of the island. Our work shows the existence of Majorana sweet spots, even when the island is not tuned at a charge-degeneracy point. In contrast to the Kitaev chains in grounded superconductors, these sweet spots involve a degeneracy between states with a well-defined number of particles.