In monolayer transition-metal dichalcogenide semiconductors, many-body correlations can manifest in optical spectra when photoexcited electron-hole pairs (excitons) are introduced into a 2D Fermi sea of mobile carriers. At low carrier densities, the formation of positively and negatively charged excitons (X±) is well documented. However, in WSe2 monolayers, an additional absorption resonance, often called X−′, emerges at high electron density. Its origin is not understood. Here we investigate the X−′ state via polarized absorption spectroscopy of electrostatically-gated WSe2 monolayers in high magnetic fields to 60~T. Field-induced filling and emptying of the lowest optically-active Landau level in the K′ valley causes repeated quenching of the corresponding optical absorption. Surprisingly, however, these quenchings are accompanied by absorption changes to higher-lying Landau levels in both K′ and K valleys, which are unoccupied. These results cannot be reconciled within a single-particle picture, and demonstrate the many-body nature and inter-valley correlations of the X−′ quasiparticle state.
@article{arxiv.2201.00780,
title = {Many-body exciton and inter-valley correlations in heavily electron-doped WSe$_2$ monolayers},
author = {Jing Li and Mateusz Goryca and Junho Choi and Xiaodong Xu and Scott A. Crooker},
journal= {arXiv preprint arXiv:2201.00780},
year = {2022}
}