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Updated: Jun 28, 2025

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Quantum Beats between Spin-Singlet and Spin-Triplet Interlayer Exciton Transitions in WSe₂-MoSe₂ Heterobilayers

Mehmet Atıf Durmuş¹, Ibrahim Sarpkaya¹

¹Bilkent University UNAM - National Nanotechnology Research Center, Ankara 06800, Turkey.

|April 19, 2024

Abstract:

The long-lived interlayer excitons (IXs) of semiconducting transition metal dichalcogenide heterobilayers are prime candidates for developing various optoelectronic and valleytronic devices. Their photophysical properties, including fine structure, have been the focus of recent studies, and the presence of two spin states, namely, spin-singlet and spin-triplet, has been experimentally confirmed. However, the existence of the interaction between these states and their nature remains unknown to date. Here, we demonstrate the presence of coherent coupling between the spin-singlet and spin-triplet IXs of a WSe₂-MoSe₂ heterobilayer utilizing quantum beat spectroscopy via a home-built Michelson interferometer. As a clear signature of coherent coupling, the quantum beat signal has been observed for the first time between closely spaced transitions of IXs. The observed strong damping of the quantum beat signals with fast dephasing times of 270-400 fs indicates that fluctuations giving rise to inhomogeneous broadening in the photoluminescence emission of these states are uncorrelated.

Keywords:

coherence dephasing time heterobilayer interlayer exciton quantum beats singlet triplet

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