Dark excitons: Energetics, dynamics, transport and correlated phases

Principal investigators

  1. Marcel Reutzel, I. Physikalisches Institut, Georg-August-Universität Göttingen
  2. Stefan Mathias, I. Physikalisches Institut, Georg-August-Universität Göttingen [webpage]

teaser picture

Abstract

Excitations in transition metal dichalcogenide (TMD) heterostructures are strongly dominated by the formation of Coulomb correlated electron-hole pairs, i.e., excitons. In many cases, the energetically most stable excitons are optically dark, i.e., momentum-indirect or spin-forbidden. While this indirect nature makes the excitons highly relevant because of their elongated lifetime, the respective energy landscape and dynamics cannot be easily accessed. Likewise, the interaction of the dark excitons with the emergent moiré potential or the transport properties of excitons can only be accessed indirectly. We will use momentum microscopy to be directly sensitive to the spatio-temporal dynamics of optically bright and dark excitons in TMD heterostructures.

We and a few other groups world-wide have developed a new type of time- and angle-resolved photoelectron spectroscopy experiment (trARPES), momentum microscopy. We have shown that momentum microscopy can be applied to exfoliated and twisted TMD heterostructures. trARPES experiments can be used to quantify the energy landscape and ultrafast dynamics of excitons on the length- and time-scales of nanometers and femtoseconds.