报告题目：Force Detection and Frequency Fluctuations in Carbon Nanotube Mechanical Resonators
报 告 人：Joel Moser, Institute of Photonic Sciences (ICFO), Barcelona
报告摘要：Carbon nanotubes allow studying a broad range of phenomena, from many-electron transport in one-dimensional systems to nonlinear dynamics and fluctuations of bending modes. They also provide unique tools for mass and charge measurements with unprecedented sensitivity [1,2]. Another important new application is force measurement . I will present our recent force sensing experiments in which our nanotube mechanical resonators display quality factors as high as 5 million, and experience a force noise as low as 10-21 N Hz-1/2 . This force noise has a thermal origin and is associated with the Brownian motion of the nanotube at a temperature of 0.04 K. To detect the low amplitude vibrations of the nanotube in the Brownian motion regime at such a low temperature, we employ an ultrasensitive method based on correlated electrical noise measurements, in combination with parametric down-conversion.
The nanotube dynamics is also affected by non-thermal fluctuations. They lead to a broadening of the resonant response beyond the decay-rate value. We developed a simple technique to extract the decay rate that does not involve complicated ring-down measurements . It relies on the interplay of periodic driving and frequency fluctuations in the displacement spectrum of the nanotube resonator. We find that the intrinsic quality factors of nanotube resonators may even surpass the values we measure.
Force sensing with nanotube resonators may offer new opportunities for detecting and manipulating individual nuclear spins.
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 J. Moser, J. Güttinger, A. Eichler, M. J. Esplandiu, D. E. Liu, M. I. Dykman, and A. Bachtold, Nature Nanotech.8, 493 (2013).
 J. Moser, A. Eichler, J. Güttinger, M. I. Dykman, and A. Bachtold, Nature Nanotech.9, 1007 (2014).
 Y. Zhang, J. Moser, J. Güttinger, A. Bachtold, and M. I. Dykman, Phys. Rev. Lett. 113, 255502 (2014).
Dr. Joel Moser is working as a senior research assistant in Institute of Photonic Sciences (ICFO), Barcelona, since December 2006. His main research activities over the past few years have revolved about the physics of nanomechanical systems made of graphene and carbon nanotubes. His other research topics include the transport properties of chemically modified graphene exposed to ozone, the electrostatic environment of graphene probed by Electrostatic Force Microscopy, and the current-induced cleaning of graphene.