Microscopic Theory of Optical Excitations in Interface-Dominated Material Systems

Summary

This project deals with the microscopic modelling of electron-hole-pair excitations in interface dominated semiconductor materials. We plan to analyze the optically linear and nonlinear response and the formation dynamics of spatially inhomogeneous excitons (type-II or charge-transfer excitons) where the constituting electrons and holes are located in neighbouring material regions that are separated by an internal interface.

As model systems, we will focus (i) on semiconductor heterostructures with type-II band alignment and (ii) van-der Waals bonded heterostructures consisting of quasi-two-dimensional layers of transition-metal dichalcogenides (TMDC). We will concentrate on the properties of the interface specific charge-transfer (CT) excitations and plan to investigate the build-up of interface specific correlations as well as the CT exciton formation dynamics after optical excitation, the related excitonic nonlinearities, as well as the terahertz (THz) response of the optically excited semiconductor systems. In the TMDCs, we will extend our fully relativistic treatment of their excitonic properties and the interface specific modifications in heterostructure arrangements.

Project-related publications

1. L. Meckbach, T. Stroucken, S.W. Koch
   Influence of the effective layer thickness on the groundstate and excitonic properties of transition-metal dichalcogenide systems
   Phys. Rev. B 97, 035425 (2018).
2. C.E. Stevens, T. Stroucken, A.V. Stier, J. Paul, H. Zhang, P. Dey, S.A. Crooker, S.W. Koch, D. Karaiskai
   Superradiant Coupling Effects in Transition-Metal Dichalcogenides
   Optica 5, 749 (2018).
3. L. Meckbach, J. Hader, U. Huttner, J. Neuhaus, J.T. Steiner, T. Stroucken, J.V. Moloney, S.W. Koch
   Ultrafast band-gap renormalization and build-up of optical gain in monolayer MoTe₂
   Phys. Rev. B 101, 075401 (2020).
4. I. Kilen, M. Kolesik, J. Hader, J.V. Moloney, U. Huttner, M.K. Hagen, S.W. Koch
   Propagation induced dephasing in semiconductor high-harmonic generation
   Phys. Rev. Lett. 125, 083901 (2020).
5. M. Borsch, C.P. Schmid, L. Weigl, S. Schlauderer, N. Hofmann, C. Lange, J.T. Steiner, S.W. Koch, R. Huber, M. Kira
   Super-resolution lightwave tomography of electronic bands in quantum materials
   Science 370, 1204 (2020).