Ballistic dynamics of flexural thermal movements in a nanomembrane revealed with subatomic resolution

• Main Authors: Liu, Tongjun, Ou, Jun-Yu, Papasimakis, Nikitas, MacDonald, Kevin F., Gusev, Vitalyi E., Zheludev, Nikolay I.
• Other Authors: School of Physical and Mathematical Sciences
• Format: Article
• Language: English
• Published: 2023
• Subjects: Science::Physics; Flexural Modes; Freestanding Films
• Online Access: https://hdl.handle.net/10356/164372
• Institution: Nanyang Technological University

Flexural oscillations of freestanding films, nanomembranes, and nanowires are attracting growing attention for their importance to the fundamental physical and optical properties and device applications of two-dimensional and nanostructured (meta)materials. Here, we report on the observation of short-time scale ballistic motion in the flexural mode of a nanomembrane cantilever, driven by thermal fluctuation of flexural phonons, including measurements of ballistic velocities and displacements performed with subatomic resolution, using a free electron edge-scattering technique. Within intervals <10 μs, the membrane moves ballistically at a constant velocity, typically ~300 μm/s, while Brownian-like dynamics emerge for longer observation periods. Access to the ballistic regime provides verification of the equipartition theorem and Maxwell-Boltzmann statistics for flexural modes and can be used in fast thermometry and mass sensing during atomic absorption/desorption processes on the membrane.