Highly Tunable and Strong Bound Exciton in MoSi2N4 via Strain Engineering

TL;DR

This study uses advanced computational methods to analyze excitonic properties in MoSi2N4, revealing highly tunable, strongly bound excitons influenced by strain, with potential for robust optoelectronic applications.

Contribution

It provides the first detailed theoretical investigation of excitons in MoSi2N4, highlighting their strong binding energy and strain sensitivity, which was not previously characterized.

Findings

Excitons in MoSi2N4 have a binding energy up to 0.95 eV.

Optical bandgap is 2.44 eV and sensitive to tensile strain.

Excitonic properties are highly tunable via strain, with marginal change in binding energy.

Abstract

Motivated by the recently synthesized layered material MoSi2N4, we investigated excitonic response of quasiparticle of monolayer MoSi2N4 by using G0W0 and Bethe-Salpeter equation (BSE) calculations. With a dually sandwiched structure consisting of a central MoN2 layer analogue of 2H-MoS2 capped with silicon-nitrogen (SiN) honeycomb outer layers, MoSi2N4 possesses frontier orbitals confined at the central MoN2 layer with similar sub-valley at K-point as 2H-MoS2. The valley splitting (~130 meV) due to the spin-orbital coupling (SOC) gives rise to a doublet in the spectrum. Excitons in MoSi2N4 shows a strong binding energy up to 0.95 eV with the optical bandgap of 2.44 eV. Both electronic and optical gaps are highly sensitive to tensile strains and become redshift albeit a marginal change of exciton binding energy. With the protection of capped SiN layers, quantum confined excitons in MoSi2N4 without the need of additional passivation layer like BN would provide a bright new platform for robust emission with partially screened disturbance from environment.