title: High Quality Factor Mechanical Resonators Based on WSe2 Monolayers.
abstract: 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.
authors.affiliation: ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology , 08860 Castelldefels Barcelona, Spain.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Morell
authors.affiliation: ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology , 08860 Castelldefels Barcelona, Spain.
authors.forename: Antoine
authors.initials: A
authors.lastname: Reserbat-Plantey
authors.affiliation: ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology , 08860 Castelldefels Barcelona, Spain.
authors.forename: Ioannis
authors.initials: I
authors.lastname: Tsioutsios
authors.affiliation: ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology , 08860 Castelldefels Barcelona, Spain.
authors.forename: Kevin G
authors.initials: KG
authors.lastname: Schädler
authors.affiliation: INSP, Paris 6 Jussieu , 75006 Paris, France.
authors.forename: François
authors.initials: F
authors.lastname: Dubin
authors.affiliation: ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology , 08860 Castelldefels Barcelona, Spain.
authors.forename: Frank H L
authors.initials: FH
authors.lastname: Koppens
authors.affiliation: ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology , 08860 Castelldefels Barcelona, Spain.
authors.forename: Adrian
authors.initials: A
authors.lastname: Bachtold
keywords: 2D materials; NEMS; Nanomechanical resonators; WSe2; optomechanics; transition metal-dichalcogenides (TMD)