0000000000530469
AUTHOR
Henrique Pereira Coutada Miranda
Exciton-Phonon Coupling in the Ultraviolet Absorption and Emission Spectra of Bulk Hexagonal Boron Nitride
We present an \textit{ab initio} method to calculate phonon-assisted absorption and emission spectra in the presence of strong excitonic effects. We apply the method to bulk hexagonal BN which has an indirect band gap and is known for its strong luminescence in the UV range. We first analyse the excitons at the wave vector $\overline{q}$ of the indirect gap. The coupling of these excitons with the various phonon modes at $\overline{q}$ is expressed in terms of a product of the mean square displacement of the atoms and the second derivative of the optical response function with respect to atomic displacement along the phonon eigenvectors. The derivatives are calculated numerically with a fin…
Strong Exciton-Coherent Phonon Coupling in Single-Layer MoS2
Broadband transient absorption with sub-20fs temporal resolution, supported by ab-initio calculations, quantitatively provides the strength of exciton-coherent phonon coupling in 1L-MoS2, showing a resonant profile around the C exciton.
Interlayer and intralayer excitons in MoS2/WS2 and MoSe2/WSe2 heterobilayers
Accurately described excitonic properties of transition metal dichalcogenide heterobilayers (HBLs) are crucial to comprehend the optical response and the charge carrier dynamics of them. Excitons in multilayer systems possess an inter- or intralayer character whose spectral positions depend on their binding energy and the band alignment of the constituent single layers. In this paper, we report the electronic structure and the absorption spectra of ${\mathrm{MoS}}_{2}/{\mathrm{WS}}_{2}$ and ${\mathrm{MoSe}}_{2}/{\mathrm{WSe}}_{2}$ HBLs from first-principles calculations. We explore the spectral positions, binding energies, and the origins of inter- and intralayer excitons and compare our re…
Strongly Coupled Coherent Phonons in Single-Layer MoS 2
We present a transient absorption setup combining broadband detection over the visible-UV range with high temporal resolution ($\sim$20fs) which is ideally suited to trigger and detect vibrational coherences in different classes of materials. We generate and detect coherent phonons (CPs) in single layer (1L) MoS$_2$, as a representative semiconducting 1L-transition metal dichalcogenide (TMD), where the confined dynamical interaction between excitons and phonons is unexplored. The coherent oscillatory motion of the out-of-plane $A'_{1}$ phonons, triggered by the ultrashort laser pulses, dynamically modulates the excitonic resonances on a timescale of few tens fs. We observe an enhancement by…