Corrections to the RPA Dielectric Function Induced by Fluctuations in the Momentum Distribution

TL;DR

This paper introduces a new dielectric function that accounts for fluctuations in the momentum distribution, especially relevant for nonideal systems, extending the generalized RPA and traditional RPA models.

Contribution

It presents a novel dielectric function that incorporates momentum distribution fluctuations, improving upon the generalized RPA for nonideal systems.

Findings

Reduces to generalized RPA when fluctuations are small

Further reduces to traditional RPA for ideal momentum distributions

Highlights importance of fluctuations in nonideal systems

Abstract

In this article, we introduce a new dielectric function that is different even from the generalised RPA, first introduced in cond-mat/9810043, in that it pays attention to fluctuations in the momentum distribution. We argued that this is important when the momentum distribution is very nonideal. This new dielectric function reduces to the generalised RPA when the number-fluctuations are small, and the generalised RPA in turn reduces to the traditional RPA dielectric function when the momentum distribution is close to ideal.