Engineering the eigenstates of coupled spin-1/2 atoms on a surface

TL;DR

This paper demonstrates precise engineering and control of coupled spin-1/2 atoms on a surface using atomic placement and ESR, enabling exploration of quantum many-body phenomena.

Contribution

It introduces a controllable spin-1/2 system on a surface with tunable interactions, combining atomic precision placement and ESR for quantum state manipulation.

Findings

Mapping of interactions from dipole to exchange coupling

Precise tuning of superposition states with STM tip

Potential for studying quantum many-body systems

Abstract

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 (ESR) 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 exploration of quantum many-body systems based on networks of spin-1/2 atoms on surfaces.