A Chemist's Perspective on the Necklace-Diamond Chain; A quasi-1D quantum simulator hosting compact localised edge states

Abstract

We can use artificial atoms created by manipulating CO chemisorbed on atomically flat Cu(111) at 5 K to form artificial molecules. Unlike real molecules, artificial molecules can be made for non equilibrium geometries. We examine the quasi-1D necklace-diamond chain, an artificial molecule that hosts compact localised states on both ends. Compact localised end states are highly localised eigenstates of the Hamiltonian, that are more strongly localised than the topological end states found in the Su-Schrieffer-Heeger chain. The presence of compact localised states on three atoms of each end of the necklace-diamond lattice is theoretically proven using the tight-binding model and density functional theory, and experimentally verified using scanning tunnelling spectroscopy. We show that manipulating the coupling strength of the first atom to the bulk of the chain alters the exact localisation of the compact localised end state.