Ten Haaf Sebastiaan L D, Zhang Yining, Wang Qingzhen, Bordin Alberto, Liu Chun-Xiao, Kulesh Ivan, Sietses Vincent P M, Prosko Christian G, Xiao Di, Thomas Candice, Manfra Michael J, Wimmer Michael, Goswami Srijit
QuTech and Kavli Institute of NanoScience, Delft University of Technology, Delft, The Netherlands.
Department of Physics and Astronomy, Purdue University, West Lafayette, IN, USA.
Nature. 2025 May;641(8064):890-895. doi: 10.1038/s41586-025-08892-5. Epub 2025 Apr 30.
A chain of quantum dots (QDs) in semiconductor-superconductor hybrid systems can form an artificial Kitaev chain hosting Majorana bound states (MBSs). These zero-energy states are expected to be localized on the edges of the chain, at the outermost QDs. The remaining QDs, comprising the bulk, are predicted to host an excitation gap that protects the MBSs at the edges from local on-site perturbations. Here we demonstrate this connection between the bulk and edges in a minimal system, by engineering a three-site Kitaev chain in a two-dimensional electron gas. Through direct tunnelling spectroscopy on each site, we show that the appearance of stable zero-bias conductance peaks at the outer QDs is correlated with the presence of an excitation gap in the middle QD. Furthermore, we show that this gap can be controlled by applying a superconducting phase difference between the two hybrid segments and that the MBSs are robust only when the excitation gap is present. We find a close agreement between experiments and the original Kitaev model, thus confirming key predictions for MBSs in a three-site chain.
半导体 - 超导体混合系统中的量子点链可以形成承载马约拉纳束缚态（MBS）的人工基塔耶夫链。这些零能态预计会局域在链的边缘，即最外层的量子点上。构成主体的其余量子点预计会有一个激发能隙，该能隙可保护边缘处的MBS免受局部在位微扰的影响。在此，我们通过在二维电子气中构建一个三格点基塔耶夫链，在一个最小系统中展示了主体与边缘之间的这种联系。通过对每个格点进行直接隧穿光谱测量，我们表明，外层量子点处稳定的零偏置电导峰的出现与中间量子点中激发能隙的存在相关。此外，我们表明，通过在两个混合段之间施加超导相位差可以控制这个能隙，并且只有当存在激发能隙时，MBS才是稳健的。我们发现实验与原始基塔耶夫模型之间有密切的一致性，从而证实了对三格点链中MBS的关键预测。
