Quantitative analog simulation of molecular orbitals in a scanning tunneling microscope

Synthetic quantum systems offer a pathway to explore the physics of complex quantum matter in a programmable fashion. This approach becomes particularly advantageous when it comes to systems that are chemically unstable and thermodynamically unfavorable. Using CO quantum corrals in a cryogenic scanning tunneling microscope, we emulate molecular structures of planar organic molecules, including anti-aromatic and non-Kekulé species that are generally reactive or unstable. Spectroscopic images of such synthetic molecules correspond well with molecular orbitals obtained from ab-initio calculations. The quantitative nature of our analogue simulators is demonstrated by faithful extraction of bond orders and global aromaticity indices, which are otherwise technically daunting using real molecules. This approach opens new possibilities in quantum physics and chemistry, particularly in the study of designer nanostructures, due to the high degree of flexibility and reconfigurability.