Majorana bound states in one-dimensional nanowires have attracted wide attention in recent years due to their potential use as  qubits for topological quantum computation based on braiding. However, a key feature of this quantum system relies on the localization lengths of the bound states. Scientists at the University of Basel have assembled mono-atomic iron chains on the surface  of superconducting lead Pb(110) and combined for the first time scanning tunneling microscopy and atomic force microscopy to spatially characterize the chains down to the atomic scale.

The Majorana bound states appear as a zero-energy mode in the STM and as a pronounced halo in the AFM measurement at 5K, disappear above the superconducting state of lead and are well-localized at the chain ends (25 nm) with two localization lengths and wave function oscillations as predicted by theory. These observations thus lend strong support to the existence of Majorana bound states in hybrid Fe/Pb systems and provide strong motivation to use them as qubits for  quantum computing devices.

Author(s): Rémy Pawlak, Marcin Kisiel, Jelena Klinovaja, Tobias Meier, Shigeki Kawai, Thilo Glatzel, Daniel Loss and Ernst Meyer