Enhanced Linear Dichroism of Flattened-Edge Black Phosphorus Nanoribbons

TL;DR

This paper demonstrates that reconstructing the edges of black phosphorus nanoribbons flattens their lattice, significantly enhances their linear dichroism, and alters optical absorption, opening new avenues for optoelectronic applications.

Contribution

The study reveals a novel edge reconstruction in black phosphorus nanoribbons that enhances linear dichroism and modifies optical properties, with potential applications in photonics.

Findings

Edge reconstruction introduces a new valence band.

Flattened edges increase linear dichroism in visible spectrum.

Significant alteration of optical absorption due to edge effects.

Abstract

Black phosphorus is a material with an intrinsic anisotropy in electronic and optical properties due to its puckered honeycomb lattice. Optical absorption is different for incident light with linear polarization in the armchair and zigzag directions (linear dichroism). These directions are also used in the cuts of materials to create black phosphorus nanoribbons. Edges of nanoribbons usually have small reconstruction effects, with minor electronic effects. Here, we show a reconstruction of the armchair edge that introduces a new valence band, which flattens the puckered lattice and increases the linear dichroism extrinsically in the visible spectrum. This enhancement in linear dichroism is explained by the polarization selection rule, which considers the parity of the wave function to a reflection plane. The flattened-edge reconstruction originates from the inversion of chirality of the P atoms at the edges and significantly alters the entire optical absorption of the material. The flattened edges have potential applications in pseudospintronics, photodetectors and might provide new functionalities in optoelectronic and photonic devices.