Distinct moir\'e trions in a twisted semiconductor homobilayer

TL;DR

This paper reports the discovery of unique charge-transfer trions in twisted TMD bilayers, revealing complex many-electron states influenced by moiré patterns and valley-specific behaviors, with implications for quantum technologies.

Contribution

It introduces a new type of charge-transfer trion in TMD homobilayers, highlighting their internal structure and dependence on twist angle and doping, advancing understanding of moiré excitonic physics.

Findings

Observation of charge-transfer trions with distinct real-space localization.

Identification of electron-hole pairs in different valleys (K and Gamma).

Dependence of trion properties on twist angle and doping levels.

Abstract

Many fascinating properties discovered in graphene and transition metal dichalcogenide (TMD) moir\'e superlattices originate from flat bands and enhanced many-body effects. Here, we discover new many-electron excited states in TMD homobilayers. As optical resonances evolve with twist angle and doping in MoSe$_2$ bilayers, a unique type of ``charge-transfer" trions is observed when gradual changes in atomic alignment between the layers occur. In real space, the optically excited electron-hole pair mostly resides in a different site from the doped hole in a moir\'e supercell. In momentum space, the electron-hole pair forms in the single-particle-band $K$-valley, while the hole occupies the $\Gamma$-valley. The rich internal structure of this trion resonance arises from the ultra-flatness of the first valence band and the distinct influence of moir\'e potential modulation on holes and excitons. Our findings open new routes to realizing photon-spin transduction or implementing moir\'e quantum simulators with independently tunable fermion and boson densities.