14 research outputs found
Crossover from Electronic to Atomic Shell Structure in Alkali Metal Nanowires
After making a cold weld by pressing two clean metal surfaces together, upon
gradually separating the two pieces a metallic nanowire is formed, which
progressively thins down to a single atom before contact is lost. In previous
experiments [1,2] we have observed that the stability of such nanowires is
influenced by electronic shell filling effects, in analogy to shell effects in
metal clusters [3]. For sodium and potassium at larger diameters there is a
crossover to crystalline wires with shell-closings corresponding to the
completion of additional atomic layers. This observation completes the analogy
between shell effects observed for clusters and nanowires.Comment: 4 page
Observation of Supershell Structure in Alkali Metal Nanowires
Nanowires are formed by indenting and subsequently retracting two pieces of
sodium metal. Their cross-section gradually reduces upon retraction and the
diameters can be obtained from the conductance. In previous work we have
demonstrated that when one constructs a histogram of diameters from large
numbers of indentation-retraction cycles, such histograms show a periodic
pattern of stable nanowire diameters due to shell structure in the conductance
modes. Here, we report the observation of a modulation of this periodic
pattern, in agreement with predictions of a supershell structure.Comment: Phys. Rev. Lett., in prin