UV active plasmons in alkali and alkaline earth intercalated graphene

TL;DR

This study uses ab initio Density Functional Theory to reveal UV-active plasmons in alkali and alkaline earth intercalated graphene, showing their potential for sensing applications due to their optical activity.

Contribution

It demonstrates the emergence of UV-active, optically active plasmons in chemically doped graphene, a phenomenon not observed in other materials.

Findings

Four prominent plasmon modes identified in doped graphene

Inter-layer plasmons are optically active and suitable for sensing

Doping dramatically alters graphene's excitation spectrum in the UV range

Abstract

The interband pi and pi+sigma plasmons in pristine graphene and the Dirac plasmon in doped graphene are not applicable, since they are broad or weak, and weakly couple to an external longitudinal or electromagnetic probe. Therefore, the ab initio Density Function Theory is used to demonstrate that the chemical doping of the graphene by the alkali or alkaline earth atoms dramatically changes the poor graphene excitation spectrum in the ultra-violet frequency range (4 - 10 eV). Four prominent modes are detected. Two of them are the intra-layer plasmons with the square-root dispersion, characteristic for the two-dimensional modes. The remaining two are the inter-layer plasmons, very strong in the long-wavelength limit but damped for larger wave-vectors. The optical absorption calculations show that the inter-layer plasmons are both optically active, which makes these materials suitable for small organic molecule sensing. This is particularly intriguing because the optically active two-dimensional plasmons have not been detected in other materials.