Conductance Oscillations in Zigzag Platinum Chains

Using first principles simulations we perform a detailed study of the structural, electronic, and transport properties of monatomic platinum chains, sandwiched between platinum electrodes. First, we demonstrate that the most stable atomic configuration corresponds to a zigzag arrangement that gradually straightens as the chains are stretched. Second, we find that the averaged conductance shows slight parity oscillations with the number $n$ of atoms in the chain. Additionally, the conductance of chains of fixed $n$ oscillates as the end atoms are pulled apart, due to the gradual closing and opening of conductance channels as the chain straightens.

Figure 1

(a) Cohesive energy $E_c$ and (b) number of open scattering channels at the Fermi energy $N(E_{\mathrm{F}})$ of platinum chains as a function of $d_z$. Number of open scattering channels $N(E)$ as a function of energy $E$ calculated at (c) $d_z=2.38$ and (d) $d_z=2.15\AA$ for zigzag (solid line) and linear (dashed line) chains.

Figure 2

The different chains connecting (001) oriented fcc leads studied in this Letter: (a) 4-atom chain, (b) single atom contact, and (c) 2-atom chain. $d_z$ is the distance between leads.

Figure 3

Cohesion curves of the chain plus leads systems, for zigzag and linear chains of two atoms (circles and squares, respectively), and zigzag chains containing 3, 4, and 5 atoms (triangles, diamonds, and stars, respectively). All curves have been shifted in energy in order to align the local minima.

Figure 4

Conductance of platinum chains. (a) Two atoms in zigzag or linear arrangement (circles or squares, respectively). (b) Three atoms; in the inset is plotted the tail of the curve in a logarithmic scale that shows the tunneling behavior when the chain breaks.

Figure 5

(a) Evolution of the conductance of 2, 3, 4, and 5 atom chains as a function of $d_z$ (circles, triangles, diamonds, and stars, respectively). (b) Conductance vs the number of atoms in the chain measured at the equilibrium distance (crosses) and averaged over a range of 2 Å about such distance (squares).