Electronic polarity of nanoclusters: quantum and many-body effects

TL;DR

This paper investigates the quantum and many-body effects influencing the electrical polarity of nanoclusters, revealing conditions under which polarizability exceeds classical expectations and highlighting the limitations of traditional screening models.

Contribution

It provides a detailed quantum mechanical analysis of nanocluster polarizability, including numerical solutions for two-electron systems and corrections to screening approximations.

Findings

Quantum effects can enhance nanocluster polarizability beyond classical limits.

Many-body screening reduces polarizability, but RPA overestimates this effect in few-electron systems.

Numerical solutions agree with models at high densities and reveal quantum oscillations at low densities.

Abstract

Interesting electrical polarity in nanoclusters usually requires the polarizability to exceed the value R^3 of the classical sphere of radius R. We clarify how this occurs naturally in single electron quantum systems, and relate it to the giant polarizability of Na_14F_13, and to spontaneous dipole formation on niobium clusters. Many-body effects generally reduce the polarizability through screening. The usual RPA treatment retrieves the classical answer, but it significantly overestimates screening in few-electron systems. The system of two electrons on the surface of a sphere is solved numerically, to account for the Coulomb repulsion. At high densities, numerical results agree with RPA model with properly subtracted self-interaction effects. At low densities, the system performs quantum oscillations around the classical ground state. We calculate the lowest anharmonic correction to the polarizability, which also agrees well with numerical evaluation of the polarizability.