Phonon-mediated exciton capture in Mo-based transition metal dichalcogenides

Electron Dynamics in a Two-Dimensional Nanobubble: A Two-Level System Based on Spatial Density

“…We then set up the equation of motion for the density matrix including the carrier–phonon interaction. In particular, here we account for the electron–phonon interaction with longitudinal optical (LO) phonons of energy ℏω LO = 46.3 meV via the Fröhlich coupling. , We use a Lindblad formalism including all nondiagonal density matrix elements accounting for the spatial inhomogenity in our system, capturing most effects found also in quantum kinetics calculations (for more details see refs , , , and and Supporting Information). We note that for the traveling wave packet we consider coherent dynamics in contrast to diffusion dynamics already observed in experiments. ,,− Here, in fact we address the dynamics in the very first few hundreds of femtoseconds at very low temperature, where TMDCs show scattering times of several picoseconds and energy-thermalization time scales of tens of picoseconds, as recently experimentally observed for related excitons via phonon-assisted photoluminescence, cf.…”

Terahertz-Induced Energy Transfer from Hot Carriers to Trions in a MoSe2 Monolayer

“…Now, we discuss other possible effects of the THz radiation on the MoSe 2 monolayer. First of all, we notice that the pump–probe signal is not due to heating of the monolayer lattice via FEL absorption or via substrate heating, inducing Varshni and Polaron shifts of the exciton and trion resonances, , for two reasons: (1) heating of the lattice would not explain why the signal at the trion energy is around 1 order of magnitude higher than the signal at the exciton energy; (2) the differential signals at the exciton and at the trion energies would be expected to have the same time constants. To get a more quantitative proof, we have measured the dependence of the trion and exciton energies on the lattice temperature (see SI), showing that the trion and the exciton resonances undergo similar redshift with increasing lattice temperature.…”

“…The first term accounts for the exciton resonance, where is the excitonic coupling strength, the electron occupation is treated in thermal approximation, that is, is the Fermi–Dirac distribution where E F ( n , T ) is the Fermi level, E X = E g + E B X is the excitonic transition energy, which is given by the band gap E g and the binding energy of the exciton E B X . γ X is introduced to account for the homogeneous broadening of the exciton. ,,, The Hartree–Fock term δ E is given by with the 2D screened Coulomb potential V q . ,, The two addends in eq are the reduction of the exciton binding energy (blueshift) and the reduction of the band gap (redshift) due to the presence of carriers in the conduction band. With the Coulomb potential used in our calculation (see SI), an increase of the carrier temperature induces a decrease of this term and, therefore, leads to a redshift of the exciton energy.…”

“…The kinetic energy transfer , where M X is the exciton mass, originates from the energy and momentum conservation during the trion formation process as we discussed above. γ T is introduced to take into account an homogeneous broadening of the exciton and trion resonances. ,,, …”

Excitonic theory of doping-dependent optical response in atomically thin semiconductors

“…Concurrently, the simplicity of our theory allows further adaptations, for instance, to study the trion dynamics in optical wave mixing experiments [98][99][100][101][102] or photoluminescence [103][104][105][106] influenced by phonon-assisted relaxation phenomena [107,108]. Further perspectives could be to theoretically investigate the influence of doping on spatiotemporal dynamic effects not only in monolayer TMDCs [109][110][111][112][113][114][115][116] but also in other atomically thin semiconductors like hybrid perovskites [117][118][119].…”