Recently, a new exciton species of quadrupole exciton (QX) has been discovered in two-dimensional (2D) transition-metal dichalcogenide (TMD) heterotrilayers, which has attracted increasing attention for its fascinating properties. Theoretically, it is predicted that QXs will be squeezed into energetically favored staggered dipole excitons (Stg-DXs) as the exciton density increases. Here, we report photoluminescence spectroscopy studies of this exciton transition between QXs and Stg-DXs in ${\mathrm{WSe}}_2/{\mathrm{MoSe}}_2/{\mathrm{WSe}}_2$ heterotrilayers. As the exciton density increases, we observe that the Stark effect curve gradually deforms from a hyperbola to a piecewise linear function, providing the first sign of the transition. At the same time, the initially dark QXs become radiative, reaffirming the transition from QXs to Stg-DXs, as the optical selection rules are lifted by breaking the mirror symmetry. Remarkably, we find that this transition can be tuned by introducing doping to change the screening and thus the interactions between excitons. Our results provide observations and understanding of QXs and Stg-DXs in TMD heterotrilayers.

Close

PrevNext

View figure in article

• Excitons
• Orthoexcitons
• Transition metal dichalcogenides
• Twisted heterostructures