Plasmon-induced nonlinear response of silver atomic chains.

Area of Science:

• * Condensed matter physics
• * Quantum chemistry
• * Materials science

Background:

• * Understanding the nonlinear optical response of low-dimensional metallic systems is crucial for developing advanced optoelectronic devices.
• * Linear atomic chains exhibit unique plasmonic properties that can be sensitive to external stimuli.
• * Ultrafast laser excitation provides a powerful tool to probe dynamic electronic processes in materials.

Purpose of the Study:

• * To investigate the real-time nonlinear response of a linear silver atomic chain under ultrafast laser excitation.
• * To elucidate the underlying mechanisms responsible for the observed nonlinear phenomena, including the role of plasmons and electron excitation.
• * To explore how factors like molecular adsorption and chain length influence the nonlinear optical properties.

Main Methods:

• * Time-dependent density functional theory (TDDFT) simulations were employed to model the system's behavior.
• * Analysis focused on the tunneling current to quantify nonlinear responses.
• * Investigated the impact of plasmon excitation, Landau damping, and molecular adsorption on electronic dynamics.

Main Results:

• * Observed nonlinear responses up to the fifth order in the tunneling current.
• * Attributed nonlinear effects to high-energy electron excitation via Landau damping of plasmons.
• * Demonstrated enhanced nonlinear effects upon adsorption of polar molecules (e.g., water) and with increasing atomic chain length.

Conclusions:

• * The study reveals significant nonlinear optical phenomena in linear silver atomic chains driven by ultrafast lasers.
• * Findings highlight the role of plasmonic effects and electron dynamics in generating high-order nonlinear responses.
• * Results provide fundamental insights for controlling plasmon-induced nonlinearities at the atomic scale.