Tuning exciton complexes in twisted bilayer WSe2 at intermediate misorientation

Abstract

Twist angle modifies the band alignment, screening, and interlayer (IL) coupling in twisted bilayers (tBLs) of transition metal dichalcogenides. Intermediate misorientation (twist angles > 15 degrees) bilayers (BLs) offer a unique opportunity to tune excitonic behavior within these concurrent physical mechanisms but are seldom studied. In this paper, we measure many-body excitonic complexes in monolayer (ML), natural BL, and tBL WSe2. Neutral biexciton (XX) is observed in tBL, while being undetected in nonencapsulated ML and BL, demonstrating unique effects of disorder screening in tBLs. The XX as well as charged biexciton are robust to thermal dissociation and are controllable by electrostatic doping. Vanishing of momentum-indirect IL excitons with increasing electron doping is demonstrated in tBL, resulting from the near alignment of Q-K and K-K valleys. Intermediate misorientation samples offer a high degree of control of excitonic complexes while offering possibilities for studying exciton-phonon coupling, band alignment, and screening.

References in corpus (11)

• Quantum ESPRESSO: a modular and open-source software project for quantum simulations of materials
• Tightly bound excitons in monolayer WSe2
• Observation of Moiré Excitons in WSe2/WS2 Heterostructure Superlattices
• Resonantly hybridised excitons in moiré superlattices in van der Waals heterostructures
• Evolution of Interlayer Coupling in Twisted MoS2 Bilayers
• Moiré excitons: from programmable quantum emitter arrays to spin-orbit coupled artificial lattices
• Valley Phonons and Exciton Complexes in a Monolayer Semiconductor
• Emerging Photoluminescence from the Dark-Exciton Phonon Replica in Monolayer WSe2
• Momentum-Dark Intervalley Exciton in Monolayer Tungsten Diselenide Brightened via Chiral Phonon
• Hybridized intervalley moiré excitons and flat bands in twisted WSe${}_2$ bilayers
• Exciton dynamics in WSe2 bilayers