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R. G. Herb Condensed Matter Seminar
Detecting frequency fluctuations in mesoscopic oscillators
Date: Thursday, November 5th
Time: 10:00 am
Place: Chamberlin 5310
Speaker: Yaxing Zhang, Michigan State University
Abstract: Mesoscopic oscillators, such as nanomechanical resonators or optomechanical systems, usually experience comparatively large fluctuations due to their small size. An important type of fluctuations is frequency fluctuations, that is, the oscillator eigenfrequency is subject to a random perturbation in time. For nanomechanical resonators, frequency fluctuations can come from tension and mass fluctuations, fluctuating charges in the substrate, or dispersive inter-mode coupling; for electromagnetic cavity modes, they can come from fluctuations of dielectric constant. Frequency fluctuations lead to the broadening of oscillator linewidth. However, this broadening is partly masked by the broadening due to oscillator decay, making the identification of frequency noise difficult. In this talk, I will show that the interplay of a resonant driving and frequency noise can lead to specific features in the oscillator power spectrum that allow sensitive detection and quantitive characterization of frequency noise. I will start with a generic analysis of a harmonic oscillator with frequency noise, corroborated by measurements on a carbon nanotube resonantor [1]. Then I will discuss a particular type of frequency noise that comes from dispersive inter-mode coupling based on microscopic descriptions [2].

[1] Zhang, Y., Moser, J., GĂĽttinger, J., Bachtold, A. & Dykman, M. I. Interplay of driving and frequency noise in the spectra of vibrational systems. Phys. Rev. Lett. 113, 255502 (2014).
[2] Zhang, Y. & Dykman, M. I. Spectral effects of dispersive mode coupling in driven mesoscopic systems. Phys. Rev. B 92, 165419 (2015).

Host: Vavilov
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