Engineering the Eigenstates of Coupled Spin-1/2 Atoms on a Surface

• Published in: Physical review letters 2017-12, Vol.119 (22), p.227206-227206, Article 227206
• Main Authors: Yang, Kai, Bae, Yujeong, Paul, William, Natterer, Fabian D, Willke, Philip, Lado, Jose L, Ferrón, Alejandro, Choi, Taeyoung, Fernández-Rossier, Joaquín, Heinrich, Andreas J, Lutz, Christopher P
• Format: Article
• Language: English
• ISSN: 0031-9007; 1079-7114
• DOI: 10.1103/PhysRevLett.119.227206

Quantum spin networks having engineered geometries and interactions are eagerly pursued for quantum simulation and access to emergent quantum phenomena such as spin liquids. Spin-1/2 centers are particularly desirable, because they readily manifest coherent quantum fluctuations. Here we introduce a controllable spin-1/2 architecture consisting of titanium atoms on a magnesium oxide surface. We tailor the spin interactions by atomic-precision positioning using a scanning tunneling microscope (STM) and subsequently perform electron spin resonance on individual atoms to drive transitions into and out of quantum eigenstates of the coupled-spin system. Interactions between the atoms are mapped over a range of distances extending from highly anisotropic dipole coupling to strong exchange coupling. The local magnetic field of the magnetic STM tip serves to precisely tune the superposition states of a pair of spins. The precise control of the spin-spin interactions and ability to probe the states of the coupled-spin network by addressing individual spins will enable the exploration of quantum many-body systems based on networks of spin-1/2 atoms on surfaces.