In Pursuit of 2D Materials for Maximum Optical Response

TL;DR

This paper investigates the theoretical optical limits of 2D materials, identifying candidates with exceptional broadband reflectance and absorption for use in ultra-thin optoelectronic devices across various wavelengths.

Contribution

It provides a comprehensive theoretical and computational analysis of the maximum optical response of 2D materials, highlighting new materials with superior optical properties.

Findings

2D boron exhibits >99% broadband reflectance in >100 layers

Several monolayer semiconductors have >30% absorbance across different ranges

Predicted 2D materials suitable for ultra-thin optical devices

Abstract

Despite being only a few atoms thick, single-layer two-dimensional (2D) materials display strong electron-photon interactions that could be utilized in efficient light modulators on extreme subwavelength scales. In various applications involving light modulation and manipulation, materials with strong optical response at different wavelengths are required. Using qualitative analytical modeling and first-principles calculations, we determine the theoretical limit of the maximum optical response such as absorbance (A) and reflectance (R) in 2D materials and also conduct a computational survey to seek out those with best A and R in various frequency ranges, from mid-infrared (IR) to deep ultraviolet (UV). We find that 2D boron has broadband reflectance R >99% for >100 layers, surpassing conventional thin films of bulk metals such as silver. Moreover, we identify 2D monolayer semiconductors with maximum response, for which we obtain quantitative estimates by calculating quasiparticle energies and accounting for excitonic effects by solving the Bethe-Salpeter equation (BSE). We found several monolayer semiconductors with absorbances >30% in different optical ranges which are more than half of the maximum possible value for a 2D material. Our study predicts 2D materials which can potentially be used in ultra-thin reflectors and absorbers for optoelectronic application in various frequency ranges.