Large and high quality single crystals of the new unconventional superconductor LiFeAs were grown by a new approach using the self-flux technique. Both energy dispersive X-ray spectroscopy and inductively coupled plasma mass spectroscopy revealed a stoichiometric Li/Fe/As composition. Measurements of the magnetic susceptibility reveal the superconducting transition at T C = 17 K with a very sharp ΔT C and a 100% shielding fraction and, thus, bulk superconductivity. This sharp transition is also found by measurements of the specific heat and by measurements of the temperature dependence of the resistivity. Nuclear quadrupole resonance (NQR) spectroscopy reveals a very sharp resonance line, with a much smaller line width than reported for all other FeAs superconductors, confirming the high ordering of the LiFeAs single crystals also on a local scale.

Stepped Cu nanostripes with varying terrace widths are self-assembled during Ag-induced periodic faceting of vicinal Cu(111). By changing Ag coverage the average terrace size within individual Cu stripes is readily tuned, making it possible to select the one-dimensional or two-dimensional character of surface states. Furthermore, the average terrace size can be smoothly switched from 10 to 30 A, thereby tracking the transition from step-lattice, quasi-two-dimensional umklapp bands to terrace-confined one-dimensional quantum well states.

No abstract

Adsorption of submonolayer amounts of Ag on vicinal Cu(111) induces periodic faceting. The equilibrium structure is characterized by Ag-covered facets that alternate with clean Cu stripes. In the atomic scale, the driving force is the matching of Ag(111)-like packed rows with Cu(111) terraces underneath. This determines the preference for the facet orientation and the evolution of different phases as a function of coverage. Both Cu and Ag stripe widths can be varied smoothly in the 3-30 nm range by tuning Ag coverage, allowing to test theoretical predictions of elastic theories. * Corresponding author. Electronic address: