Resonant Coupling of a Moiré Exciton to a Phonon in a WSe₂/MoSe₂ Heterobilayer

Abstract

Moirépatterns with an angular mismatch in van der Waals heterostructures are a fascinating platform to engineer optically generated excitonic properties. The moirépattern can give rise to spatially ordered exciton ensembles, which offer the possibility for coherent quantum emitters and quantum simulation of many-body physics. The intriguing moiréexciton properties are affected by their dynamics and exciton−phonon interaction. Here, we report the moiréexciton and phonon interaction in a twisted WSe 2 /MoSe 2 heterobilayer. By tuning the excitation energy, we realized the selective excitation of the moiréexciton at phonon resonances and the otherwise negligible small absorption. Furthermore, we revealed the relaxation of moiréexciton ensembles between different potential minima via the resonant phonon scattering process. Our findings highlight resonant coupling of a moiréexciton to a phonon and could pave a new way for the exploration of novel quantum phenomena of the moireé xciton.

Observation of moiré excitons in the twisted WS2/WS2 homostructure

“…As the laser power increases, the flat minibands are sequentially filled from the low-energy level to the high-energy level and gradually reach saturation, which is consistent with previous reports. 42 The results show that the modulation of the intralayer excitons by the reconstructed moiré potential weakens with the increase in power.…”

“…As the power increases, the flat electronic minibands in the reconstructed moiré potential are sequentially filled with trapped excitons from the low-energy level to high-energy level and finally reach saturation, which is manifested as a decrease in the exciton peak and an increase in the peak width on the PL spectrum. 42 can be distinguished at low power (less than 0.1 mW). In addition, as the laser power increases, the number of peaks in the PL spectrum gradually decreases and finally become a main peak.…”

Electrically Tunable Localized versus Delocalized Intralayer Moiré Excitons and Trions in a Twisted MoS2 Bilayer

“…Gate-Tunable MoiréExciton-Resonant Raman Scattering. Recent studies highlight emerging coupling mechanisms between the moiréexcitons and phonons 27,28 which can play an important role in the dynamics of moiréexciton ensembles. Using tBL-MoS 2 , here we demonstrate tunable resonant Raman scattering by means of electrically controlled oscillator strength of moiréexcitons discussed in the previous section.…”

Valley Relaxation of the Moiré Excitons in a WSe2/MoSe2 Heterobilayer

“…Let us discuss the excitonic energy levels in the moiré potential to understand the resonance features. In contrast to the excitation of the WSe 2 layer, as shown in Figure , the excitation energy is close to the moiré exciton energy inside the moiré potential, and the resonance feature originates from phonon resonance . Here, we revealed a very sharp PLE peak at ∼25 meV excess energy arising from phonon resonance in addition to a relatively broad peak with a few meV spectral widths.…”

“…This result suggests that the resonant Raman process is enhanced when the initially excited state is a real triplet moiré state, as shown in Figure e,f. The amplitude change of the sharp components in Figure a indicates the inhomogeneous distribution of the moiré exciton involved in the process (see Supporting Information). The resonant Raman process reveals the intravalley relaxation of the moiré exciton in twisted semiconducting heterobilayers.…”