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Neutral and Charged Inter-Valley Biexcitons in Monolayer MoSe2



Lixiang Xu, Judith Specht, Philip Nagler, Kha Tran, Akshay Singh, Chandriker K. Dass, Andreas Knorr, Xiaoqin Li, Galan Moody


In atomically thin transition metal dichalcogenides (TMDs), reduced dielectric screening of the Coulomb interaction leads to strongly correlated many-body states, including excitons and trions, that dominate the optical properties. Higher-order states, such as bound biexcitons, are possible but are difficult to identify unambiguously using linear optical spectroscopy methods alone. Here, we implement polarization-resolved two-dimensional coherent spectroscopy to unravel the complex optical response of monolayer MoSe2 and identify multiple higher-order correlated states. Decisive signatures of neutral and charged inter-valley biexcitons appear in cross-polarized two- dimensional spectra as distinct resonances with respective 20 meV and 5 meV binding energies—similar to recent calculations using variational and Monte Carlo methods. A theoretical model taking into account the valley-dependent optical selection rules reveals the specific quantum pathways that give rise to these states. Inter-valley biexcitons identified here—comprised of neutral and charged excitons from different valleys—offer new opportunities for creating exotic exciton-polariton condensates and for developing ultrathin biexciton lasers and polarization-entangled photon sources.
Nature Communications


two-dimensional materials, transition metal dichalcogenides, biexcitons, ultrafastspectroscopy


Xu, L. , Specht, J. , Nagler, P. , Tran, K. , Singh, A. , Dass, C. , Knorr, A. , Li, X. and Moody, G. (2017), Neutral and Charged Inter-Valley Biexcitons in Monolayer MoSe2, Nature Communications, [online],, (Accessed May 17, 2024)


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Created June 27, 2017, Updated October 12, 2021