First-principles study of luminescence in hexagonal boron nitride single layer: Exciton-phonon coupling and the role of substrate

Lechifflart, Pierre; Paleari, Fulvio; Sangalli, Davide; Attaccalite, Claudio

doi:10.1103/physrevmaterials.7.024006

Cited by 10 publications

(11 citation statements)

References 63 publications

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“…To comprehend excitonic thermalization, we employ a similar fitting approach, as demonstrated by Cassabois et al, to the falling edge of the spectra, employing an exponential Boltzmann factor with an effective temperature T eff . From the plot depicting T eff against the lattice temperature T lat (see Figure ), it becomes evident that the excitons thermalize with the crystal beyond 25 K. This observation aligns with a recently reported case concerning emission spectra from monolayer h-BN …”

Section: Resultssupporting

confidence: 89%

“…Hence, to speed up the convergence, we interpolated the phonon energies on a dense q grid of 60 × 60 × 1. A smooth Fourier interpolation (“double-grid approach”) can then be used to interpolate the electronic energies at k + q . , We therefore fixed the course grid at 12 × 12 × 1 and converged the quasi-particle energy gap for a variety of dense q grids (see Figure S16 in the SI for the quasiparticle gap convergence with respect to q -grids).…”

Section: Computational Methodologymentioning

confidence: 99%

“…From the plot depicting T eff against the lattice temperature T lat (see Figure 6), it becomes evident that the excitons thermalize with the crystal beyond 25 K. This observation aligns with a recently reported case concerning emission spectra from monolayer h-BN. 34 Phonon-assisted emission can also be understood from the presence of phonon replicas, as depicted in panel a of Figure 5. These replicas are more pronounced at low temperatures.…”

Section: Indirect Excitons and Photoluminescence Emission In 2d H-wcmentioning

confidence: 99%

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Phonon Assisted Exciton Processes in Two-Dimensional Tungsten Monocarbide

Saraswat,

Kolos,

Verma

et al. 2024

J. Phys. Chem. C

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In this study, we utilized a rigorous ab initio-based finite momentum Bethe−Salpeter equation to investigate the photoluminescence emission in two-dimensional hexagonal tungsten carbide (h-WC). This thermodynamically stable monolayer exhibits an indirect optical gap, resulting in phonon-assisted emission. We observe that light absorption is a direct process centered around the direct quasiparticle gap, while light emission is indirect and requires modes between Γ−M in the phonon dispersion. The emission lines feature prominent phonon replicas at cryogenic temperatures, particularly nearinfrared wavelengths (1.09 and 1.17 eV), and we observe exciton thermalization with the crystal beyond 25 K. Additionally, nonradiative recombination is a remarkably fast process, on the order of a few femtoseconds (4.8 fs at 0 K and 2.8 fs at 300 K), compared to radiative recombination (2.3 ps at 0 K and 214 ns at 300 K). These optical characteristics of 2D h-WC may facilitate the promise of photon-emitter devices for near-infrared signal communication.

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Section: Resultssupporting

confidence: 89%

Section: Computational Methodologymentioning

confidence: 99%

Section: Indirect Excitons and Photoluminescence Emission In 2d H-wcmentioning

confidence: 99%

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Phonon Assisted Exciton Processes in Two-Dimensional Tungsten Monocarbide

Saraswat,

Kolos,

Verma

et al. 2024

J. Phys. Chem. C

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“…Beside a direct-gap opening of 2.8 eV at the K -point of the first BZ, quasi-particle (QP) corrections to the Kohn–Sham band structure also induce a direct-indirect band gap transition due to a nearly free-electron conduction state at Γ descending below the bottom of the conduction band at K . Our findings are consistent with previous works , (see the SI for additional details). The same behavior is observed when excitonic effects are included through the BSE: as can be seen from the excitonic band structure in Figure a, the energy of the indirect exciton at q = K ( E K (1) ) is 30 meV below the energy of the direct exciton ( E Γ (1) ).…”

supporting

confidence: 94%

“…At this point, it is important to note that recent first-principles MBPT calculations have suggested that the interaction with the substrate, which is always present in real experiments, pushes the nearly free-electron band at Γ above the bottom of the conduction band at K , making m-BN a direct gap semiconductor . Under these conditions, phonon satellites below the QP peak should be essentially absent, in contrast with experimental observations. , Based on our analysis of the exc-ph coupling, a possible explanation for the phonon satellites observed in the experimental spectra is that m-BN is actually a multivalley semiconductor consisting of two nearly degenerate exciton valleys, namely, E Γ (1) and E K (2) .…”

mentioning

confidence: 59%

Optical Absorption and Photoluminescence of Single-Layer Boron Nitride from a First-Principles Cumulant Approach

Marini,

Calandra,

Cudazzo

2024

Nano Lett.

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The photoluminescence spectrum of a single-layer boron nitride remains elusive, marked by enigmatic satellites that hint at significant but unidentified exciton–phonon coupling. Here, by employing a first-principles approach based on the many-body cumulant expansion of the charge response, we calculate the optical absorption and photoluminescence of a single-layer boron nitride. We identify the specific exciton–phonon scattering channels and unravel their impact on the optical absorption and photoluminescence spectra, thereby providing an interpretation of the experimental features. Finally, we show that, even in a strongly polar material such as h-BN monolayer, the electron–hole interaction responsible for the excitonic effect results in the cancellation of the Frölich interaction at small phonon momenta. This effect is captured only if the invariance of the exciton–phonon matrix elements under unitary transformations in the Bloch function manifold is preserved in the calculation.

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Phonon-Mediated Exciton Relaxation in Two-Dimensional Semiconductors: Selection Rules and Relaxation Pathways

Zhang,

Xie,

Wang

et al. 2024

J. Phys. Chem. Lett.

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Exciton−phonon coupling (ExPC) is crucial for energy relaxation in semiconductors, yet the first-principles calculation of such coupling remains challenging, especially for two-dimensional (2D) systems. Here, an accurate method for calculating ExPC is developed and applied in exciton relaxation problems in monolayer WSe 2 . Considering the interplay between the exciton wave functions and electron−phonon coupling (EPC) matrix elements, we find that ExPC shows selection rules distinct from the ones of EPC. By employing the Wannier exciton model, we generalize these selection rules, which state that the angular quantum numbers of the exciton must match the winding numbers of the EPC matrix elements for the ExPC to be allowed. To verify our theory and method, we calculate intervalley exciton relaxation pathways, which agree well with a recent experiment. * sı Supporting InformationThe Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.jpclett.4c01433. Details of GW-BSE calculations, electron−phonon scattering, exciton−phonon scattering, and exciton scattering times (PDF)

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First-principles study of luminescence in hexagonal boron nitride single layer: Exciton-phonon coupling and the role of substrate

Cited by 10 publications

References 63 publications

Phonon Assisted Exciton Processes in Two-Dimensional Tungsten Monocarbide

Phonon Assisted Exciton Processes in Two-Dimensional Tungsten Monocarbide

Optical Absorption and Photoluminescence of Single-Layer Boron Nitride from a First-Principles Cumulant Approach

Phonon-Mediated Exciton Relaxation in Two-Dimensional Semiconductors: Selection Rules and Relaxation Pathways

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