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 WSe2/MoSe2/WSe2 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.

中文翻译：

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WSe2/MoSe2/WSe2异质三层中四极杆和交错偶极子夹层激子之间的过渡


最近，在二维 （2D） 过渡金属二硫化物 （TMD） 异质三层中发现了一种新的四极激子 （QX） 激子物种，其迷人的特性引起了越来越多的关注。从理论上讲，随着激子密度的增加，预计 QX 将被挤压到能量偏好的交错偶极子激子 （Stg-DXs） 中。在这里，我们报道了 WSe2/MoSe2/WSe2 异质三层中 QXs 和 Stg-DXs 之间这种激子跃迁的光致发光光谱研究。随着激子密度的增加，我们观察到 Stark 效应曲线逐渐从双曲线变形为分段线性函数，提供了过渡的第一个迹象。同时，最初较暗的 QX 变为辐射，再次确认了从 QX 到 Stg-DX 的过渡，因为光学选择规则通过打破镜子对称性而解除。值得注意的是，我们发现可以通过引入掺杂来改变筛选，从而改变激子之间的相互作用，从而调整这种转变。我们的结果提供了对 TMD 异质三层中 QXs 和 Stg-DXs 的观察和理解。