Project Details
Projekt
Dipolar excitons and interlayer coupling: Optics, dynamics and transport in Janus TMD heterostructures
Applicants
Professor Dr. Ermin Malic; Professor Dr. Andrey Turchanin; Professor Dr. Bernhard Urbaszek
Subject Area
Experimental Condensed Matter Physics
Term
since 2024
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 535253440
The vertical stacking of the atomically thin transition metal dichalcogenides (TMDs) into van der Waals heterostructures allows the realization of a plethora of physical phenomena and technological applications. The interface between these two materials dictates the emergent properties, which can be tuned through choice of material, twisting and electric fields. A radical approach to alter the behaviour of these interfaces is to chemically modify the constituent layers. TMDs monolayers consist of a transition metal layer between two chalcogen layers. Therefore, by substituting one of these chalcogen layers with a different one, it is possible to grow a "Janus" TMD, as for example MoSe2 becomes SeMoS. The inherent dipole in Janus TMDs is expected to drastically alter their interfacial behaviour in Janus-based TMD heterostructures (Janus HSs), modulating the interlayer distance, the wave function hybridization, and the moiré potential in twisted systems. Another consequence of the built in-dipole is that the exciton-phonon interaction is believed to be enhanced. Therefore, we expect that Janus HSs could facilitate extremely efficient phonon-driven interlayer exciton formation, minimizing radiative losses. Furthermore, we expect a highly interesting exciton transport in Janus HSs: On one side the enhanced moiré potentials and the increased exciton-phonon scattering are likely to hinder the propagation of excitons, but on the other side the inherent dipole will certainly lead to an efficient exciton-exciton repulsion giving rise to a faster exciton transport. Currently, Janus HSs are poorly understood, with only a handful of experimental and theoretical studies. In this proposal we will undertake a joint experiment-theory collaboration combining state-of-the-art CVD growth with sophisticated optical characterization and microscopic many-particle theory to reveal intriguing phenomena in exciton optics, dynamics and transport in Janus HSs. In particular, we will (i) explore the role stacking order, choice of material, twist-angle, temperature and electric field have on the optical fingerprint of intra- and interlayer excitons in Janus HSs, (ii) reveal the exciton formation, relaxation and decay in Janus HSs, where the long radiative lifetime, enhanced phonon-scattering and inherent electric dipole will be of crucial importance, and (iii) explore the exciton transport and determine how the moiré potential can be modulated to either trap or release excitons through tuning the stacking order and twist angle in Janus HSs. We envision to offer a comprehensive microscopic understanding of exciton optics, dynamics and transport in Janus-based TMD heterostructures revealing pathways towards external tunability and control of these many-particle phenomena that are also highly relevant for optoelectronic applications based on Janus TMD materials.
DFG Programme
Priority Programmes
