Exciton

About: Exciton is a research topic. Over the lifetime, 31603 publications have been published within this topic receiving 810642 citations.

Approaching the strong coupling limit in single plasmonic nanorods interacting with J-aggregates

Abstract: We studied scattering and extinction of individual silver nanorods coupled to the J-aggregate form of the cyanine dye TDBC as a function of plasmon - exciton detuning. The measured single particle spectra exhibited a strongly suppressed scattering and extinction rate at wavelengths corresponding to the J-aggregate absorption band, signaling strong interaction between the localized surface plasmon of the metal core and the exciton of the surrounding molecular shell. In the context of strong coupling theory, the observed "transparency dips" correspond to an average vacuum Rabi splitting of the order of 100 meV, which approaches the plasmon dephasing rate and, thereby, the strong coupling limit for the smallest investigated particles. These findings could pave the way towards ultra-strong light-matter interaction on the nanoscale and active plasmonic devices operating at room temperature.

How dielectric screening in two-dimensional crystals affects the convergence of excited-state calculations: Monolayer MoS 2

Abstract: We present first-principles many-body calculations of the dielectric constant, quasiparticle band structure, and optical absorption spectrum of monolayer MoS${}_{2}$ using a supercell approach. As the separation between the periodically repeated layers is increased, the dielectric function of the layer develops a strong $q$ dependence around $q=0$. This implies that denser $k$-point grids are required to converge the band gap and exciton binding energies when large supercells are used. In the limit of infinite layer separation, here obtained using a truncated Coulomb interaction, a $45\ifmmode\times\else\texttimes\fi{}45$ $k$-point grid is needed to converge the ${G}_{0}{W}_{0}$ band gap and exciton energy to within 0.1 eV. We provide an extensive comparison with previous studies and explain agreement and variations in the results. It is demonstrated that too coarse $k$-point sampling and the interactions between the repeated layers have opposite effects on the band gap and exciton energy, leading to a fortuitous error cancellation in the previously published results.

Excitons in anisotropic solids: The model of fractional-dimensional space

Abstract: Wannier-Mott excitons in anisotropic or confined systems are studied using the model of fractional-dimensional space. The excitons in an anisotropic solid are treated as ones in an isotropic fractional-dimensional space, where the dimension is determined by the degree of anisotropy. By solving the simple hydrogenic Schr\"odinger equation in the fractional-dimensional space, exciton wave functions, bound energies, and associated optical spectra are obtained as a function of spatial dimensionality. Dimensional behavior in binding energy, radial density, and angular momentum is discussed. The model provides a quantitative measure of anisotropy by a fractional dimension, as viewed from exciton dynamics, which can be determined experimentally from interband optical spectra. The results obtained here are also applicable to hydrogenic impurities in anisotropic solids.

Study of the Photoluminescence of Phosphorus-Doped p-Type ZnO Thin Films Grown by Radio-Frequency Magnetron Sputtering

Abstract: Phosphorus-doped p-type ZnO thin films were grown on sapphire by radio-frequency magnetron sputtering. The photoluminescence (PL) spectra revealed an acceptor bound exciton peak at 3.355 eV and a conduction band to the acceptor transition caused by a phosphorus related level at 3.310 eV. A study of the dependence of the excitation laser power density and temperature on the characteristics of the PL spectra suggests that the emission lines at 3.310 and 3.241 eV can be attributed to a conduction band to the phosphorus-related acceptor transition and a donor to the acceptor pair transition, respectively. The acceptor energy level of the phosphorus dopant was estimated to be located 127 meV above the valence band.

Structural dependence of excitonic optical transitions and band-gap energies in carbon nanotubes.

Abstract: The optical transitions of semiconducting carbon nanotubes have been ascribed to excitons. Here we use two-photon excitation spectroscopy to measure exciton binding energies, as well as band-gap energies, in a range of individual species of semiconducting SWNTs. Exciton binding energies are large and vary inversely with nanotube diameter, as predicted by theory. Band-gap energies are significantly blue-shifted from values predicted by tight-binding calculations.