Coherent coupling between neutral and charged exciton

Monolayers of transition metal dichalcogenides (TMDs) can host various many-body quasiparticles due to the high binding energy of the excitons. In the presence of free carriers in the monolayer, the optically generated neutral exciton can easily transfer its oscillator strength to form charged excitons. Depending on the optical selection rule, charged excitons can be formed by a combination of three (trion), five (quinton), or even a higher number of quasiparticles. Charged excitons are particularly interesting in two-dimensional (2D) systems due to their tunability in spectral resonance and oscillator strength via external electrical control [1]. Additionally, the formation of these quasiparticles can be coherently controlled via resonant coupling between neutral and charged states [2]. This can be observed by monitoring the population of charged excitons increasing by orders of magnitude under exciton resonance. This interdependence led to a non-monotonic increase in carrier density of charged excitons under enhanced n-doping with increasing gate voltage. Also, the valley polarization of the charged excitons is shown to be more susceptible under moderate to high scattering under the influence of exchange interactions in the motional narrowing regime. These observations open new avenues for the development of valleytronics devices [3] and advance our understanding of valley-based switching for quantum information processing.

*Corresponding author: kejgoh@yahoo.com

References

[1] Das, Sarthak, et al., ACS Nano 16.6: 9728-9735 (2022).

[2] Hao, Kai, et al., Nano letters 16.8: 5109-5113 (2016).

[3] Goh et al., Advanced Quantum Technologies 3, 1900123 (2020).