Spatiotemporal dynamics of Coulomb-correlated carriers in semiconductors

摘要

When the excitation of carriers in real space is focused down to the nanometer scale, the carrier system can no longer be viewed as homogeneous, and ultrafast transport of the excited carrier wave packets occurs. In state-of-the-art semiconductor structures such as low-dimensional heterostructures or monolayers of transition-metal dichalcogenides, the Coulomb interaction between excited carriers becomes stronger due to confinement or reduced screening. This demands a fundamental understanding of strongly interacting electrons and holes and the influence of Coulomb correlations. To study the corresponding particle dynamics in a controlled way, we consider a system of up to two electron-hole pairs exactly within a wave-function approach. We show that the excited wave packets contain a nontrivial mixture of free-particle and excitonic states. We further scrutinize the influence of the Coulomb interaction on the wave-packet dynamics, revealing its different role for below- and above-band-gap excitation.