Interfacial Control of Dark-Exciton–Magnon Coupling in CrSBr via C₆₀ Adsorption
This project investigates how molecular interfaces can be used to control the interplay between excitons and magnetic excitations in the two-dimensional antiferromagnetic semiconductor CrSBr. Of particular interest are dark excitons—optically forbidden states that become observable through their coherent coupling to collective excitations. Our approach combines controlled functionalization of CrSBr with C₆₀ molecules and broadband ultrafast spectroscopy. We will determine how molecular adsorption modifies bright and dark excitons, magnetic anisotropy, magnon dynamics, and the coupling between excitonic and magnetic degrees of freedom.

Our recent work demonstrates that coherent GHz magnons and THz phonons both reveal a hidden excitonic resonance at 1.46 eV that is absent from steady-state optical spectra. These collective modes transiently transfer spectral weight from a nominally dark exciton into an observable optical channel. Building on this discovery, DIMEX aims to establish how molecular interfaces can tune dark excitons and their coupling to magnons, opening a route toward engineering hybrid quasiparticles in van der Waals quantum materials.