BEGIN:VCALENDAR
VERSION:2.0
PRODID:Icfo
X-PUBLISHED-TTL:P1W
BEGIN:VEVENT
UID:69e08a556199b
DTSTART:20260317T110000Z
SEQUENCE:0
TRANSP:OPAQUE
DTEND:20260317T120000Z
LOCATION:Mir-Puig Seminar Room (MP210)
SUMMARY:ICFO | EVA M. WEIG
CLASS:PUBLIC
DESCRIPTION:Doubly-clamped nanostring resonators excel as high Q nanomechan
 ical systems enabling room temperature quality factors of several 100\,000
  in the 10 MHz eigenfrequency range. Dielectric transduction via electrica
 lly induced gradient fields provides an integrated control scheme while re
 taining the large mechanical quality factor [1]. Dielectrically controlled
  nanostrings are an ideal testbed to explore a variety of dynamical phenom
 ena ranging from multimode coupling to coherent control [2]. Here we will 
 focus on the nonlinear dynamics of a single\, resonantly driven mode.\nUnd
 er strong driving conditions\, we observe an onset of self-sustained oscil
 lation in the rotating frame. This phenomenon can be attributed to a reson
 antly induced negative effective friction force (RIFF) induced by the driv
 e. The high anharmonicity of the limit cycles manifests in the generation 
 of a nanomechanical frequency comb in the power spectrum [3\, 4]. The freq
 uency comb is centered around the forced vibrations initiated at the drive
  frequency\, while the number and spacing of comb lines can be controlled 
 by the drive detuning and power. To account for a non-zero linewidth of th
 e comb lines\, we extended the theoretical model to include thermal-motion
  induced phase diffusion. This results in sub-Hz Lorentzian comb lines and
  predicts an increasing linewidth from the center to the edges of the comb
 \, scaling quadratically with the comb line index. To experimentally acces
 s the shape of the comb lines\, we have improved our measurement scheme\, 
 which was previously limited to a spectral resolution of 1 Hz. This allows
  us to capture the true form of the comb lines with mHz resolution\, and t
 o study their linewidth. We find linewidths in the sub-Hz range\, confirmi
 ng the predicted scaling with the comb line index. However\, our experimen
 tal curves cannot be described by the predicted Lorentzian lineshape. This
  is a clear indication that the phase fluctuations are not only caused by 
 thermal white noise\, but also by a mechanism with a longer time correlati
 on. We are currently working on an extended theory to include other possib
 le phase diffusion mechanisms.\nThus\, taking advantage of self-sustained 
 oscillations in a single driven nonlinear nanomechanical mode\, we explore
  phase diffusion in nanomechanical resonators. As the diffusion mechanism 
 manifests in the spectrum of a single driven mode\, this technique present
 s an orthogonal approach to previous work that relied on backaction or par
 ametrically coupled modes to induce self-sustained oscillations [5]. We ex
 pect novel insights into the nature of phase diffusion and its underlying 
 microscopic mechanisms.\n[1] &nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nb
 sp\;&nbsp\; Q. P. Unterreithmeier et al.\, Nature\, 458\, 7241 (2009).\n[2
 ] &nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\; T. Faust et al.
 \, Nat. Phys. 9\, 485&ndash\;488\, (2013).\n[3]&nbsp\;&nbsp\;&nbsp\;&nbsp\
 ;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\; J. S. Ochs et al.\, Phys. Rev. X 12\,
  041019 (2022).\n[4]&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp
 \;&nbsp\; M. I. Dykman et al.\, Phys. Rev. Lett. 122\, 254301 (2019).\n[5]
 &nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\; F. Sun et 
 al.\, Nat. Commun. 7\, 12694 (2016).
DTSTAMP:20260416T070557Z
END:VEVENT
END:VCALENDAR