Abstract: Neutral molecules with sufficiently large dipole moments can bind electrons in diffuse nonvalence orbitals with most of their charge density far from the nuclei, forming so-called dipole-bound anions. Because long-range correlation effects play an important role in the binding of an excess electron and overall binding energies are often only on the order of 10s–100s of wave numbers, predictively modeling dipole-bound anions remains a challenge. Here, we demonstrate that quantum Monte Carlo methods can accurately characterize molecular dipole-bound anions with near-threshold dipole moments. We also show that correlated sampling Auxiliary Field Quantum Monte Carlo is particularly well-suited for resolving the fine energy differences between the neutral and anionic species. These results shed light on the fundamental limitations of quantum Monte Carlo methods and pave the way toward using them for the study of weakly bound species that are too large to model using traditional electron structure methods.

Abstract: Coherent coupling between plasmons and transition dipole moments in emitters can lead to two distinct spectral effects: vacuum Rabi splitting at strong coupling strengths, and induced transparency (also known as Fano interference) at intermediate coupling strengths. Achieving either strong or intermediate coupling between a single emitter and a localized plasmon resonance has the potential to enable single-photon nonlinearities and other extreme light–matter interactions, at room temperature and on the nanometer scale. Both effects produce two peaks in the spectrum of scattering from the plasmon resonance, and can thus be confused if scattering measurements alone are performed. Here we report measurements of scattering and photoluminescence from individual coupled plasmon–emitter systems that consist of a single colloidal quantum dot in the gap between a gold nanoparticle and a silver film. The measurements unambiguously demonstrate weak coupling (the Purcell effect), intermediate coupling (Fano interference), and strong coupling (Rabi splitting) at room temperature.

Abstract: The most recent class of semiconductor nanocrystal to be synthesized colloidally is the quantum well, in which carriers are confined quantum mechanically in only one dimension. Electrons and holes in colloidal quantum wells undergo different dynamics than in either colloidal quantum dots or epitaxially grown quantum wells, providing new opportunities for applications. The opportunities presented by cadmium chalcogenide nanoplatelets are particularly exciting, because they can be grown with control over their thickness down to the single atomic layer and with all nanoplatelets in an ensemble having the same thickness. This Feature Article reviews the relaxation and recombination dynamics of electrons and holes, which are tightly bound into excitons, in nanoplatelets. These dynamics are favorable for optical gain and lasing, and this Article reviews the progress that has been made toward practical realization of nanoplatelet lasers, including the demonstration of low thresholds for room-temperature gain and lasing. Looking forward, the engineering of nanoplatelet heterostructures provides new opportunities to control carrier dynamics, opening up in particular the possibility of observing strong multiexcitonic effects at room temperature.