Highly in-plane anisotropic optical properties of fullerene monolayers

TL;DR

This study uses first-principles calculations to reveal highly in-plane anisotropic optical properties of fullerene monolayers, especially the quasi-tetragonal phase, highlighting their potential for optical applications like polarizers.

Contribution

It provides the first detailed theoretical analysis of the electronic and optical anisotropy in fullerene monolayers, especially identifying the quasi-tetragonal phase as highly anisotropic.

Findings

qHP ML is a semi-conductor with small anisotropic absorption

qTP ML is a semimetal with highly anisotropic absorption

qTP ML shows a dichroic ratio of around 12 at 0.29 eV, with strong anisotropy between 0.7 and 1.4 eV

Abstract

Both the intrinsic anisotropic optical materials and fullerene-assembled 2D materials have attracted a lot of interests in fundamental science and potential applications. The synthesis of a monolayer (ML) fullerene makes the combination of these two features plausible. In this work, using first-principles calculations, we systematically study the electronic structure, optical properties of quasi-hexagonal phase (qHP) ML and quasi-tetragonal phase (qTP) ML fullerenes. The calculations of qHP ML show that it is a semi-conductor with small anisotropic optical absorption, which agrees with the recent experimental measurements. However, the results for qTP ML reveal that it is a semimetal with highly in-plane anisotropic absorption. The dichroic ratio, namely the absorption ratio of $x$- and $y$-polarized light $\alpha$$_x$$_x$/$\alpha$$_y$$_y$, is around 12 at photon energy of 0.29 eV. This anisotropy is much more pronounced when the photon energy is between 0.7 and 1.4 eV, where $\alpha$$_x$$_x$ becomes nearly zero while $\alpha$$_y$$_y$ is more than two orders of magnitude larger. This indicates qTP ML as a candidate for long-pursuit lossless metal and a potential material for atomically thin polarizer. We hope this will stimulate further experimental efforts in the study of qTP ML and other fullerene-assembled 2D materials.