Predicting the performance of the inter-Coulombic electron capture from single-electron quantities.

The probability of the inter-Coulombic electron capture (ICEC) is studied for nanowire-embedded quantum-dot pairs where electron capture in one dot leads to electron emission from the other. Previous studies pointed to an interdependence of several ICEC pathways which can enhance the ICEC reaction probability. To identify favorable criteria for such synergies in a qualitative and quantitative manner, we conducted a considerable amount of simulations scanning multiple geometrical parameters. The focus of the paper is not only to find the geometries which are most favorable to ICEC but most importantly to explain the basic principles of the ICEC probability. We have thus derived a number of energy relations among solely single-electron level energies that explain the mechanisms of the multiple reaction pathways. Among them are direct ICEC, both slowing or accelerating the outgoing electron, as well as resonance-enhanced ICEC which captures into a two-electron resonance state that decays thereafter. These pathways may apply simultaneously for just one single geometric configuration and contribute constructively leading to an enhancement of the reaction probability. Likewise some conditions are found that clearly turn down the ICEC probability to zero. The results based on single-electron relations are so general that they can as well be used to predict the ICEC probability from the electronic structure in arbitrary physical systems such as atoms or molecules.

Quantum size effect affecting environment assisted electron capture in quantum confinements.

Ultrafast inter-Coulombic electron capture (ICEC) has been established as an important energy-transfer process in open paired-quantum-dot systems which can mediate between entrapment of free-moving electrons and release of trapped ones elsewhere by long-range electron-electron interaction within nanowires. Previous studies indicated ICEC enhancement through population and secondary decay of two-center resonance states, the latter known as inter-Coulombic decay (ICD). This study investigates the quantum-size effect of single- and double-electron states in an established model of a quasi-one-dimensional nanowire with two embedded confinement sites, represented by a pair of Gaussian wells. We analyze the ICEC related electron flux density as a function of confinement size and are able to clearly identify two distinct capture channels: a direct long-range electron-electron impulse and a conversion of kinetic energy to electron-electron correlation energy with consecutive ICD. The overlay of both channels makes ICEC extremely likely, while nanowires are a strong candidate for the next miniaturization step of integrated-circuit components.