Plasmons and screening in finite-bandwidth 2D electron gas

TL;DR

This paper investigates how finite bandwidth affects plasmons and screening in a 2D electron gas, revealing multiple plasmon branches, negative dispersion, and implications for low-loss plasmon applications.

Contribution

It provides a detailed analysis of the dynamical dielectric function in finite-bandwidth 2DEG, highlighting new plasmon behaviors and screening effects not previously characterized.

Findings

Two separate plasmon branches at small and large momenta for large bandwidth

Negative quasi-flat dispersion in the large momenta plasmon branch

Bandwidth reduction causes the two plasmon branches to merge

Abstract

The dynamical and nonlocal dielectric function of a two-dimensional electron gas (2DEG) with finite energy bandwidth is computed within random-phase approximation. For large bandwidth, the plasmon dispersion has two separate branches at small and large momenta. The large momenta branch exhibits negative quasi-flat dispersion. The two branches merge with decreasing bandwidth. We discuss how the maximum energy plasmon mode which resides at energies larger than all particle-hole continuum can potentially open a route to low-loss plasmons. Moreover, we discuss the bandwidth effects on the static screening of the charged and magnetic impurities.