We study theoretically two electron-hole pair states (biexcitons) in core/shell hetero-nanocrystals with type II alignment of energy states, which promotes spatial separation of electrons and holes. To describe Coulomb interactions in these structures, we apply first-order perturbation theory, in which we use an explicit form of the Coulomb-coupling operator that takes into account interface-po...

In photosynthesis absorbed sun light produces collective excitations (excitons) that form a coherent superposition of electronic and vibrational states of the individual pigments. Two-dimensional (2D) electronic spectroscopy allows a visualization of how these coherences are involved in the primary processes of energy and charge transfer. Based on quantitative modeling we identify the exciton-v...

Excitons in a quantum well depend on the interfacial roughness resulting from its growth. The interface is characterized by islands of size j separated by one monolayer steps across which the confining potential decreases by V0 for wider wells. A natural length is the localization length j05p\/A2MV0 characterizing the minimum size island to confine an exciton. For small islands (j,j0), the abso...

When a material is confined to one dimension, its electronic band structure can exhibit features termed van Hove singularities, which have been invoked to explain the sharp absorption spectra in materials such as single-walled carbon nanotubes (SWNTs). This model predicts a sealike photoexcited state of free electrons and holes. Recently, however, support has emerged for an exciton picture, in ...

The exciton relaxation process of CsPbI3 perovskite nanocrystals (NCs) has been investigated by using transient absorption (TA) spectroscopy. The hot exciton relaxation process is confirmed to exist in the CsPbI3 NCs, through comparing the TA data of CsPbI3 NCs in low and high energy excitonic states. In addition, the Auger recombination and intrinsic decay paths also participate in the relaxat...

Software package Mathematica is used for computer simulation of steady state fluorescence spectra of ring molecular system. The cyclic antenna unit LH2 of the bacterial photosystem from purple bacterium Rhodopseudomonas acidophila can be modeled by such system. Dynamic disorder, interaction with a bath, is included in Markovian approximation. Also three different models of uncorrelated static d...

We analyze the entanglement between two matter modes in a hybrid quantum system consisting of a microcavity, a quantum well, and a mechanical oscillator. Although the exciton mode in the quantum well and the mechanical oscillator are initially uncoupled, their interaction through the microcavity field results in an indirect exciton-mode–mechanical-mode coupling. We show that this coupling is a ...

Exciton dissociation in a donor-accepter polymer heterojunction has been simulated using a nonadiabatic molecular dynamics approach, which allows for the coupled evolution of the nuclear degrees of freedom and the electronic degrees of freedom described by multiconfigurational electronic wavefunctions. The simulations reveal important details of the charge separation process: the exciton in the...

A rate equation model for the dark and bright excitons kinetics is proposed which explains the wide variation in the observed degree of circular polarization of the PL emission in different TMDs monolayers. Our work suggests that the dark exciton states play an important, and previously unsuspected role in determining the degree of polarization of the PL emission. A dark exciton ground state pr...

Time-resolved experiments with more than one period of incoherent time evolution are becoming increasingly accessible. When applied to a two-level system, these experiments separate homogeneous and heterogeneous contributions to kinetic dispersion, i.e., to nonexponential relaxation. Here, the theory of two-dimensional (2D) multiple population-period transient spectroscopy (MUPPETS) is extended...