Exciton binding energies and luminescence of phosphorene under pressure

TL;DR

This paper investigates how uniaxial strain affects exciton binding energies and luminescence in phosphorene, revealing high exciton binding energies and strain-tunable optical properties useful for strain sensing.

Contribution

It provides a theoretical analysis of exciton stability and luminescence shifts in phosphorene under strain, highlighting the potential for strain engineering in 2D materials.

Findings

Exciton binding energy reaches 0.87 eV at 5% transverse strain.

Luminescence peak shifts linearly with strain.

Strain can be used to probe the strain state of phosphorene.

Abstract

The optical response of phosphorene can be gradually changed by application of moderate uniaxial compression, as the material undergoes the transition into an indirect gap semiconductor and eventually into a semimetal. Strain tunes not only the gap between the valence band and conduction band local extrema, but also the effective masses, and in consequence, the exciton anisotropy and binding strength. In this article, we consider from a theoretical point of view how the exciton stability and the resulting luminescence energy evolves under uniaxial strain. We find that the exciton binding energy can be as large as 0.87 eV in vacuum for 5% transverse strain, placing it amongst the highest for 2D materials. Further, the large shift of the luminescence peak and its linear dependence on strain suggest that it can be used to probe directly the strain state of single-layers.