Interlayer Valley Coupling and Hybridized Excitons in Twisted van der Waals Bilayers With Broken Translational Symmetry
Abstract
Twisted van der Waals (vdW) bilayers allow the moiré potential and interlayer coupling to be tuned through the relative rotation between layers, providing a platform to study moiré physics. At large twist angles, the lack of translational symmetry allows intralayer and interlayer valley momenta to be connected by Umklapp processes, in principle permitting unconventional intervalley coupling. However, direct experimental evidence of such couplings in twisted vdW bilayers with broken translational symmetry has been limited. Here, we observe interlayer coupling between the K and -K valleys in twisted MoS2 bilayers by detecting intense photoluminescence from high-energy interlayer hybridized excitons. These hybridized excitons are absent in commensurate twisted MoS2 homobilayers and display an almost vanishing valley Zeeman splitting, indicative of strong mixing between intralayer and interlayer excitonic states. This hybridization gives rise to an unusual magnetic-field-dependent valley polarization in excitons with distinct spin configurations. With increasing temperature, the hybridized excitons detune, and their energies approach those of intralayer excitons, revealing a sensitive interplay between moiré coupling and thermal effects. Our results uncover a key role of broken translational symmetry in excitons of twisted MoS2 bilayers and open a route to exploring quantum phenomena in aperiodic twisted MoS2 materials.
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