“Emergence of Majorana bound states in low-dimensional superconductor-magnet hybrid systems”

Dr. Howon Kim
Department of Physics, University of Hamburg

Sep. 24 (Fri.), 04:00 PM
Online seminar
https://kaist.zoom.us/j/88224188486
회의 ID: 882 2418 8486
암호: 080840

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.
First part of the talk, it will be introduced that 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.
Second, I will address experimental and theoretical studies of monolayer topological superconductivity and chiral Majorana edge modes in model-type 2D magnetic islands on elemental superconductors. In particular, we demonstrate that interface engineering by an atomically thin oxide layer is crucial for driving the studied hybrid system into a topologically non-trivial state as confirmed by theoretical calculations of the topological invariant, the Chern number.