Scanning Tunneling Microscopy Study of Quantum Cobalt Chains

We recently reported [1] on a new surface phase of the Co-vicinal-Cu(111) system, which exhibits self-assembled uniform Co quantum wires that are stable at 300K. STM images show that the wires form along the leading edge of the step rise, differentiating it from previously theoretically predicted atomic-wire phases as well as experimentally observed step-island formation. Our observations allow us to comment on the formation kinetics of the atomic-wire phase and on the fit of our data to a recently developed lattice-gas model. LT-STM measurements, taken on self-assembled Co chains, reveal a charge-density modulation that is dependent on tip bias. These charge-modulations are observed for tip-bias relatively far away from the Fermi level, both at negative and positive bias. We present arguments for the identification of these modulations as due to either charge-density-like waves (CDW) or excited states of this 1-D system. \\[4pt] [1] N. Zaki et al, Phys. Rev. B 80, 155419 (2009)