报告题目：Graphene nanomechanical resonators with quality factors exceeding 1 Million
报告人：Prof.Joel Moser， Soochow University, Suzhou, P. R. China, and Institute of Photonic Sciences (ICFO), Barcelona Spain
时 间： 2016年1月 8日（周五） 上午10:00
地 点： 南岭校区机械材料馆 209会议室
Owing to its ultra-low mass density, graphene is an interesting material for the realization of nanomechanical resonators with potential applications in mass, force and spin sensing. Such applications crucially require low intrinsic mechanical dissipation, that is, a high quality factor, because mechanical sensing is limited by the thermal noise of the resonator. Surprisingly, however, quality factors measured in graphene resonators have not exceeded 200’000, in spite of the high crystallinity of graphene sheets and much progress in fabrication techniques. To try and solve this puzzle, we have performed time-resolved energy relaxation measurements in few-layer, ultra-clean graphene resonators at cryogenic temperature. Our measurement technique consists in transducing the vibrations of the resonator by capacitively coupling the graphene sheet to a superconducting cavity, which allows us to resolve minute displacements of the sheet down to milliKelvin temperature. We coherently drive the resonator, then switch the drive off and measure the displacement oscillations as the mechanical energy freely decays. This technique is immune from frequency noise, and allows us to monitor the oscillation decay over a wide range of displacements. Our time-resolved measurements yield quality factors exceeding 1 million, within reach of quality factors measured in much larger silicon-based and diamond-based microresonators. Interestingly, quality factors estimated from additional spectral linewidth measurements are about three times smaller, indicating that such estimations are spoiled by frequency noise-induced spectral broadening. We also show that dissipation is strongly nonlinear and depends on the amplitude of the motion. Our work demonstrates that, in addition to their ultra-low mass, graphene mechanical resonators also feature very high quality factors; hence, they possess all the necessary ingredients to become excellent sensors.
Prof. Joel Moser：
Ph. D. in Physics Oct. 1999，Paris University (Orsay Campus), France
• Advisor: Prof. D. J´erome, in collaboration with Prof. W. Kang (Ewha Womans University,
Seoul, South Korea) and Prof. J. R. Cooper (Cambridge University, UK).
Specially appointed Physics professor Since Sept. 2015
Soochow University, Suzhou, P. R. China
Research Fellow, group of Prof. A. Bachtold Oct. 2012 - July 2015
Institute of Photonic Sciences (ICFO), Spain
Research Associate, group of Prof. A. Bachtold Jan. 2007 - Oct. 2012
Nanotechnology Institute of Catalonia, Spain
Postdoctoral researcher, group of Prof. J. Kotthaus Jan. 2006 - Dec. 2006
Ludwig-Maximilians University, Munich, Germany
Postdoctoral researcher, group of Prof. M. Grayson Jan. 2003 - Jan. 2006
Walter Schottky Institute, Munich, Germany
Postdoctoral researcher, group of Prof. A. Usheva Jan. 2002 - Dec. 2002
Harvard Medical School, Harvard University, USA
Publications: 35 papers published in journals such as Nature Nanotechnology, Physical Review B, Applied Physics Letters, ACS nano, Nature Communication etc.