Shape-Dependent Electronic Excitations in Metallic Chains

Abstract

The electronic excitations of silver chains with different geometries (linear, circle, arc and zigzag chains) have been investigated at the time-dependent density functional theory level, by solving the equation of motion of the reduced single-electron density matrix in the real-time domain. A scaling parameter 0 ≤ λ ≤ 1 has been introduced to adjust the two-electron contributions during propagation in the time domain in a way that allows us to distinguish different electronic excitations — plasmon and single-particle excitations. The dipole responses, in particular the plasmon resonances of these metallic chains to an external δ-pulse, show a strong dependence on their geometric structures. In most cases, the dipole responses of these chains possess great tunability when altering their geometric parameters — the radius of the circle and arc chains, and the bond angle of the zigzag chains. Some excitations in these chains also show a wide tunable excitation energy range, more than 1 eV, making it possible to fine-tune the excitations of the metallic chains at an atomic scale.