Exciton-phonon coupling and band-gap renormalization in monolayer 
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>WSe</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:math>

Mishra, Himani; Bose, Anindya; Dhar, Amit Kumar; Bhattacharya, Sitangshu

doi:10.1103/physrevb.98.045143

Cited by 33 publications

(19 citation statements)

References 57 publications

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“…To check this assumption and identify the phonon mode involved, we first perform a first-principles calculation of the phonon dispersions of monolayer WSe2. Our results show that doubly degenerate E′′ phonon modes appear with vibration energy ℏω E ′′ = 21.8 meV, consistent with previous reports 24,50,51 . This energy is in excellent agreement with our observation of the X D -X D R energy difference of 21.6 meV.…”

Section: Gate-voltage Dependent Pl Of Wse2supporting

confidence: 93%

Emerging photoluminescence from the dark-exciton phonon replica in monolayer WSe2

et al. 2019

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Tungsten-based monolayer transition metal dichalcogenides host a long-lived “dark” exciton, an electron-hole pair in a spin-triplet configuration. The long lifetime and unique spin properties of the dark exciton provide exciting opportunities to explore light-matter interactions beyond electric dipole transitions. Here we demonstrate that the coupling of the dark exciton and an optically silent chiral phonon enables the intrinsic photoluminescence of the dark-exciton replica in monolayer WSe 2 . Gate and magnetic-field dependent PL measurements unveil a circularly-polarized replica peak located below the dark exciton by 21.6 meV, equal to E″ phonon energy from Se vibrations. First-principles calculations show that the exciton-phonon interaction selectively couples the spin-forbidden dark exciton to the intravalley spin-allowed bright exciton, permitting the simultaneous emission of a chiral phonon and a circularly-polarized photon. Our discovery and understanding of the phonon replica reveals a chirality dictated emission channel of the phonons and photons, unveiling a new route of manipulating valley-spin.

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Section: Gate-voltage Dependent Pl Of Wse2supporting

confidence: 93%

Emerging photoluminescence from the dark-exciton phonon replica in monolayer WSe2

et al. 2019

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“…This result exactly matches the calculation, Equations (14) and (16), with dispersive phonons at Q = √ 0 ∕ . At the strong coupling the model with the cut-off produces the polaron shift and mass at > 2 :…”

Section: Strong Coupling: Polaron Formationsupporting

confidence: 88%

“…[11][12][13] In general, polaron effects related to the coupling of the charge carriers with in-plane polarized phonons are important for the physics of TMDC monolayers. [14][15][16][17] A remarkable property of 2D crystals is the presence of soft flexural phonon modes. [18][19][20][21] These out-of-plane vibrations are responsible for rippling and crumpling of the 2D materials as well as for their anomalous elastic properties.…”

Section: Introductionmentioning

confidence: 99%

Interlayer Exciton–Polaron in Atomically Thin Semiconductors

2020

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A novel type of exciton-phonon bound state-interlayer polaron-in a double-layer 2D semiconductor with transition metal dichalcogenides as an example, is predicted. In these systems, the interaction of the interlayer exciton with the soft modes of out-of-plane lattice vibrations caused by van der Waals forces and flexural rigidity gives rise to a bound quasiparticle. The energy and effective mass of the formed polaron for weak and strong exciton-phonon coupling regimes are calculated and analyzed. Possible manifestations of these effects in transport-and spectroscopy-related experiments are discussed.

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“…In the framework of MBPT, two self‐energy diagrams corresponding to the lowest nonvanishing terms of a perturbative treatment should be estimated. In particular, the Fan self‐energy, the first‐order term, can be written as

\sum_{n, boldk}^{Fan} ((),, ω, T) = \sum_{n^{'} boldq λ} \frac{{(||, g_{n n^{'} k}^{q λ})}^{2}}{N_{q}} ([], \frac{N_{boldq} (T) + 1 - f_{n^{'} k - q}}{ω - ε_{n^{'} k - q} - ω_{q λ} - i 0^{+}}) \times ([], \frac{N_{boldq} (T) + f_{n^{'} k - q}}{ω - ε_{n^{'} k - q} + ω_{q λ} - i 0^{+}})

where ε n , k are the DFT eigenvalues, ω q , λ are the phonon frequencies, and f n , k and N q ( T ) are the Fermi and Bose distributions of electrons and phonons, respectively. In the caser of the Debye–Waller (DW) self‐energy, corresponding to the second‐order term, it reads

\sum_{n, boldk}^{DW} ((), T) = \frac{1}{N_{q}} \sum_{boldq λ} Λ_{italicnn boldk}^{boldq λ, - boldq λ} ([], 2 N_{boldq λ} ((), T) + 1)

…”

Section: Excitonic Effects In Optical Absorption and Temperature Inflmentioning

confidence: 99%

“…In the latest work by Bhattacharya et al, band gap renormalization and electron–phonon coupling in 2D WSe 2 are comprehensively discussed . By solving a coupled electron–hole BSE taking the polaronic energies into account, results demonstrate that the in‐plane torsional acoustic phonon branch mainly accounts for the A and B exciton buildup.…”

Section: Excitonic Effects In Optical Absorption and Temperature Inflmentioning

confidence: 99%

Photoexcited charge carrier behaviors in solar energy conversion systems from theoretical simulations

Wei

Huang

Dai

2019

WIREs Comput Mol Sci

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Solar energy bears great potential in the substitution of conventional fossil fuels to enable a sustainable world. In order to harness and use solar energy, photocatalytic and photovoltaic systems made of semiconductor materials have been developed to convert sunlight into energy (electricity) based on the photoelectrochemical effects.Photoelectric events are related with the light-energy (electricity) conversion process, including photon absorption, photoexcited charge carrier separation and recombination, charge carrier transport, and photocurrent generation, as well as electron plasmonic resonance. We focus on the recent state-of-the-art simulation methods correspondingly mimicking these photogenerated charge carrier behaviors, taking electron-phonon, electron-exciton, and exciton-exciton interactions into account. Results can be obtained from the standard density function theory (DFT) for ground-state properties, many-body perturbation theory for band gap renormalization and optical absorption, time-domain DFT in combination with nonadiabatic molecular dynamics for photoexcitation dynamics, nonequilibrium Green's function and self-consistent theory for charge carrier transport properties, and classical Maxwell's equations in discrete dipole approximation for localized surface plasmon resonance absorption and near-field enhancement. In combination of the results from these simulation methods, a complete and consistent picture describing the fundamental photoelectric process in light-energy (electricity) conversion could be obtained. Simulation results offer guidelines for experimental efforts and provide new basic insights into the underlying mechanisms and the design principles for next-generation photocatalytic and photovoltaic devices of high solar light utilization efficiency.

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Exciton-phonon coupling and band-gap renormalization in monolayer WSe2

Cited by 33 publications

References 57 publications

Emerging photoluminescence from the dark-exciton phonon replica in monolayer WSe2

Emerging photoluminescence from the dark-exciton phonon replica in monolayer WSe2

Interlayer Exciton–Polaron in Atomically Thin Semiconductors

Photoexcited charge carrier behaviors in solar energy conversion systems from theoretical simulations

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