Substrate Effect on Excitonic Shift and Radiative Lifetime of Two-Dimensional Materials

TL;DR

This paper uses advanced first-principles methods to analyze how substrates influence excitonic properties and radiative lifetimes in 2D materials, providing theoretical predictions that align well with experimental results.

Contribution

It applies a reciprocal-space linear interpolation method to accurately model substrate screening effects on excitons in 2D materials at the GW level.

Findings

Substrate screening causes nonrigid shifts of excitonic peaks.

Linear relation between quasiparticle gaps and exciton binding energies.

Calculated exciton radiative lifetimes agree with experiments.

Abstract

Substrates have strong effects on optoelectronic properties of two-dimensional (2D) materials, which have emerged as promising platforms for exotic physical phenomena and outstanding applications. To reliably interpret experimental results and predict such effects at 2D interfaces, theoretical methods accurately describing electron correlation and electron-hole interaction such as first-principles many-body perturbation theory are necessary. In our previous work [Phys. Rev. B 102, 205113(2020)], we developed the reciprocal-space linear interpolation method that can take into account the effects of substrate screening for arbitrarily lattice-mismatched interfaces at the GW level of approximation. In this work, we apply this method to examine the substrate effect on excitonic excitation and recombination of 2D materials by solving the Bethe-Salpeter equation. We predict the nonrigid shift of 1s and 2s excitonic peaks due to substrate screening, in excellent agreements with experiments. We then reveal its underlying physical mechanism through 2D hydrogen model and the linear relation between quasiparticle gaps and exciton binding energies when varying the substrate screening. At the end, we calculate the exciton radiative lifetime of monolayer hexagonal boron nitride with various substrates at zero and room temperature, as well as the one of WS2 where we obtain good agreement with experimental lifetime. Our work answers important questions of substrate effects on excitonic properties of 2D interfaces.