Spin-state engineering of single titanium adsorbates on ultrathin magnesium oxide.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 41545365.
- Also identified by DOI 10.1038/s41467-026-68314-6 and PMC identifier 12905244.
- Licence recorded as CC BY-NC-ND.
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Abstract
Single atomic adsorbates on ultrathin insulating films provide a promising route towards building bottom-up quantum architectures based on atomically identical yet individually addressable spin qubits on solid surfaces. A key challenge in engineering quantum-coherent spin nanostructures lies in understanding and controlling the spin state of individual adsorbates. In this work, we investigate single titanium (Ti) atoms adsorbed on MgO/Ag(100) surfaces using a combined scanning tunneling microscopy and electron spin resonance. Our measurements reveal two distinct spin states, S = 1/2 and S = 1, depending on the local adsorption site and the thickness of the MgO film. Density functional theory calculations suggest a Ti<sup>+</sup> configuration for the Ti adsorbates with approximately 3 electrons in the 4s and 3d valence shells. Using multi-orbital magnetic multiplet calculations the site dependence of the spin can be rationalized as a charge redistribution between spin-polarizing and depolarizing orbitals. These findings underscore the potential of surface-supported single atoms as spin qubits with tunable spin and charge states, enabling atom-by-atom control in the realization of a versatile quantum platform on surfaces.