Abstract
Magnetic atoms on a superconductor give rise to Yu-Shiba-Rusinov (YSR) states within the superconducting energy gap. A spin chain of magnetic adatoms on an s-wave superconductor may lead to topological superconductivity accompanied by the emergence of Majorana modes at the chain ends. For their usage in quantum computation, it is a prerequisite to artificially assemble the chains and control the exchange couplings between the spins in the chain and in the substrate. Here, using a scanning tunneling microscope tip, we demonstrate engineering of the energy levels of the YSR states by placing interstitial Fe atoms in close proximity to adsorbed Fe atoms on an oxidized Ta surface. Based on this prototype platform, we show that the interaction within a long chain can be strengthened by linking the adsorbed Fe atoms with the interstitial ones. Our work adds an important step towards the controlled design and manipulation of Majorana end states.
Highlights
Magnetic atoms on a superconductor give rise to Yu-Shiba-Rusinov (YSR) states within the superconducting energy gap
This platform for Majorana physics has been tested almost exclusively for the substrate material Pb hampering the controlled assembly of magnetic atoms into chains or more complex networks, which are needed for braiding of Majorana modes and their usage in fault-tolerant quantum computation[3,4,5]
We introduce Fe atoms in the interstitial sites in close proximity to the Fe adatoms using the tip of a scanning tunneling microscope (STM) and demonstrate the control over the energy levels of the YSR states
Summary
Magnetic atoms on a superconductor give rise to Yu-Shiba-Rusinov (YSR) states within the superconducting energy gap. A spin chain of magnetic adatoms on an s-wave superconductor may lead to topological superconductivity accompanied by the emergence of Majorana modes at the chain ends For their usage in quantum computation, it is a prerequisite to artificially assemble the chains and control the exchange couplings between the spins in the chain and in the substrate. The recent investigation of self-assembled ferromagnetic Fe chains on superconducting Pb, featuring strong spin-orbit coupling, triggered enhanced interest in the possible realization of Majorana modes at the ends of such chains[10,11,12,13,14,15] This platform for Majorana physics has been tested almost exclusively for the substrate material Pb hampering the controlled assembly of magnetic atoms into chains or more complex networks, which are needed for braiding of Majorana modes and their usage in fault-tolerant quantum computation[3,4,5]. We extend the method to build long chains of Fe adatoms that are interacting via interstitial Fe atoms and demonstrate spin coupling within the chain
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