Seminar "Design of Majorana bound states in artificially constructed magnetic atom chains on elemental superconductors" by Dr. Howon Kim

Design of Majorana bound states in artificially constructed magnetic atom chains on elemental superconductors

by Howon Kim (Department of Physics, University of Hamburg, D-20355 Hamburg, Germany)

Abstract

Realizing Majorana bound states (MBS) in condensed matter systems is a key challenge on the way towards future topological quantum computing. As a promising platform, one-dimensional (1D) magnetic chains on conventional s-wave superconductors were theoretically predicted to host MBS at the ends of the chains. Experimentally, self-assembled ferromagnetic chains have previously been prepared on Pb substrates with limited control over the atomic-scale structure, the length, and the chemical composition of the chains [1-5].

Here, we demonstrate a new approach to design topologically non-trivial superconducting 1D magnetic chains on a conventional s-wave superconductor using single-atom manipulation techniques based on a low-temperature scanning tunneling microscope. Our artificially constructed atomic Fe chains on a Re single-crystal substrate exhibit non-collinear magnetic states and a remarkable enhancement of the zero-energy local density of states (LDOS) strongly localized at the ends of the chains. Furthermore, the enhanced zero-energy LDOS at the chain ends is shown to emerge and become stabilized with increasing chain length. Tight-binding model calculations based on parameters obtained from ab initio calculations corroborate that the system resides in the topological phase. Our work opens new pathways to design MBS in complex magnetic structures required to realize the theoretically proposed braiding of MBS with non-Abelian exchange statistics as a basis for fault-tolerant topological quantum computing.

References

[1] S. Nadj-Perge et al., Science 346, 602 (2014).

[2] M. Ruby et al., Phys. Rev. Lett. 115, 197204 (2015).

[3] R. Pawlak et al., NPJ Quantum Information 2, 16035 (2016).

[4] B. E. Feldman et al., Nature Phys. 13, 286 (2017).

[5] S. Jeon et al., Science 358, 772 (2017)