Probing Majorana localization of a phase-controlled three-site Kitaev chain with an additional quantum dot
Alberto Bordin, Florian J. Bennebroek Evertsz’, Bart Roovers, Juan D. Torres Luna, Wietze D. Huisman, Francesco Zatelli, Grzegorz P. Mazur, Sebastiaan L. D. ten Haaf, Ghada Badawy, Erik P. A. M. Bakkers, Chun-Xiao Liu, Rubén Seoane Souto, Nick van Loo, Leo P. Kouwenhoven
Abstract
Few-site implementations of the Kitaev chain offer a minimal platform to study the emergence and stability of Majorana bound states. Here, we realize two- and three-site chains in semiconducting quantum dots coupled via superconductors, and tune them to the sweet spot where zero-energy Majorana modes appear at the chain ends. We demonstrate control of the superconducting phase through both magnetic field and sweet-spot selection, and fully characterize the excitation spectrum under local and global perturbations. All spectral features are identified using the ideal Kitaev chain model. To assess Majorana localization, we couple the system to an additional quantum dot. The absence of energy splitting at the sweet spot is compatible with high-quality Majorana modes, despite the modest chain size.