Binary cobalt/copper atom chains assembled by manipulation and probed by STS

We apply STM-based atom manipulation and local tunneling spectroscopy to engineer and probe binary atom chains consisting of a magnetic and a nonmagnetic element. Utilizing single Cu and Co adatoms as building blocks, monatomic chains of various size and composition can be assembled and imaged with chemical resolution. Local spectroscopy of the electronic density of states along with a tight-binding analysis reveal significant interatomic Co-Cu coupling and the formation of confined quantum states delocalized along the entire heteroatomic chain. Co incorporation enables to tune the eigenenergy and the density of the along-chain-delocalized quantum state. These findings indicate that CoCu chains constitute a promising model system for future spin-polarized STS investigations to explore the effect of local magnetic moments incorporated into a nonmagnetic host structure.

Figure:

Constant-current image of a Cu(111) surface area with a single Cu (left) and a Co adatom (right) at 7 K (A), and contour plot of a monatomic CoCu₃CoCu₃Co chain (B). Constant-current images (37 Å x 18 Å) of a pure Cu₈ (C) and a Cu₃CoCu₄ chain (D) along with the corresponding height profiles (E). The dI/dV maps of the ground state (F) and the first (G) and second excited state (H) of the Cu₃CoCu₄ chain indicate that the Co incorporation introduces a subtle asymmetry in the lobe structure of the characteristic state densities which is well reproduced by tight-binding calculations.

Related publications:

J. Lagoute, Ch. Nacci and S. Fölsch, Doping of monatomic Cu chains with single Co atoms, Phys. Rev. Lett. 98, 146804-1/146804-4 (2007)