High Quality Factor Mechanical Resonators Based on WSe2 Monolayers.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Suspended monolayer transition metal dichalcogenides (TMDs) possess unique optical and mechanical properties, making them promising for opto-mechanical devices.
• Low measured quality factors (Q-factors) have limited the application of TMD resonators.

Purpose of the Study:

• To investigate the mechanical properties of monolayer TMD resonators at cryogenic temperatures.
• To overcome the limitations imposed by low Q-factors in TMD-based opto-mechanical systems.

Main Methods:

• Utilized an ultrasensitive optical readout technique to measure the mechanical properties of monolayer TMD resonators.
• Performed measurements at cryogenic temperatures, including liquid nitrogen and liquid helium.

Main Results:

• Monolayer WSe2 resonators exhibited a significant increase in Q-factor at cryogenic temperatures, reaching up to 4.7 × 10^4 at liquid helium temperature.
• The Q-factor of WSe2 resonators surpassed that of similar-sized monolayer graphene resonators.
• Observed a significant increase in resonant frequency upon cooling, enabling the first experimental determination of the WSe2 monolayer thermal expansion coefficient.
• High Q-factors were also observed in MoS2 and MoSe2 monolayer resonators.

Conclusions:

• Cryogenic temperatures dramatically enhance the mechanical Q-factor of monolayer TMD resonators, overcoming previous limitations.
• These high Q-factors open new avenues for quantum opto-mechanical experiments, including coupling mechanical states to excitons and quantum emitters.