Experimental Study of Temporal Coherence in 2D Spin-Forbidden Dark Excitons

Transition metal dichalcogenides (TMDs) are host to diverse excitonic physics, including a spin-forbidden ground state in tungsten based TMDs. These long lived dark excitons are a promising platform for quantum information and observing strong exciton-exciton many-body interactions. This talk reports the investigation of dark exciton coherence time in encapsulated WSe₂ monolayers. We fabricate gated heterostructure devices to control carrier concentration and use momentum resolved photoluminescence to separate dark from bright emission. Temporal coherence was extracted from both spectral linewidth analysis and using a modified Mach-Zehnder interferometer. The evolution of coherence as a function of temperature, doping, and exciton density was examined for different exciton states.  The results reveal the main competing dephasing channels and corresponding timescales, which provide insights into understanding exciton scattering dynamics in 2D.