Tuning exciton complexes in twisted bilayer <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>WSe</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:math> at intermediate misorientation
Rahul Debnath, Shaili Sett, S. Kundu, Rabindra Biswas, Varun Raghunathan, Manish Jain, Arindam Ghosh, Akshay Singh
Abstract
Twist angle modifies the band alignment, screening, and interlayer (IL) coupling in twisted bilayers (tBLs) of transition metal dichalcogenides. Intermediate misorientation (twist angles $>$ ${15}^{\ensuremath{\circ}}$) 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 ${\mathrm{WSe}}_{2}$. 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 ($X{X}^{\ensuremath{-}}$) 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 near alignment of ${Q}^{\ensuremath{'}}\text{\ensuremath{-}}K$ and $K\text{\ensuremath{-}}K$ valleys. Intermediate misorientation samples offer a high degree of control of excitonic complexes while offering possibilities of studying exciton-phonon coupling, band alignment, and screening.