ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology , 08860 Castelldefels Barcelona, Spain.
INSP, Paris 6 Jussieu , 75006 Paris, France.
Nano Lett. 2016 Aug 10;16(8):5102-8. doi: 10.1021/acs.nanolett.6b02038. Epub 2016 Aug 1.
Suspended monolayer transition metal dichalcogenides (TMD) are membranes that combine ultralow mass and exceptional optical properties, making them intriguing materials for opto-mechanical applications. However, the low measured quality factor of TMD resonators has been a roadblock so far. Here, we report an ultrasensitive optical readout of monolayer TMD resonators that allows us to reveal their mechanical properties at cryogenic temperatures. We find that the quality factor of monolayer WSe2 resonators greatly increases below room temperature, reaching values as high as 1.6 × 10(4) at liquid nitrogen temperature and 4.7 × 10(4) at liquid helium temperature. This surpasses the quality factor of monolayer graphene resonators with similar surface areas. Upon cooling the resonator, the resonant frequency increases significantly due to the thermal contraction of the WSe2 lattice. These measurements allow us to experimentally study the thermal expansion coefficient of WSe2 monolayers for the first time. High Q-factors are also found in resonators based on MoS2 and MoSe2 monolayers. The high quality-factor found in this work opens new possibilities for coupling mechanical vibrational states to two-dimensional excitons, valley pseudospins, and single quantum emitters and for quantum opto-mechanical experiments based on the Casimir interaction.
悬浮单层过渡金属二卤化物（TMD）是一种膜，其具有超低质量和卓越的光学特性，使其成为光机械应用的有趣材料。然而，到目前为止，TMD 谐振器的低测量品质因数一直是一个障碍。在这里，我们报告了一种对单层 TMD 谐振器的超灵敏光学读出方法，该方法使我们能够在低温下揭示其机械性能。我们发现，单层 WSe2 谐振器的品质因数在室温以下大大增加，在液氮温度下达到 1.6×10(4)，在液氦温度下达到 4.7×10(4)。这超过了具有类似表面积的单层石墨烯谐振器的品质因数。当冷却谐振器时，由于 WSe2 晶格的热收缩，共振频率会显著增加。这些测量使我们能够首次实验研究 WSe2 单层的热膨胀系数。基于 MoS2 和 MoSe2 单层的谐振器也具有高 Q 因子。在这项工作中发现的高 Q 因子为将机械振动状态与二维激子、谷赝自旋和单量子发射器耦合以及基于卡西米尔相互作用的量子光机械实验开辟了新的可能性。
