Catégorie : preprint

Clément Chardin, Sébastien Pairis, Stéphane Douillet, Mpïra Hocevar, Julien Claudon, Jean-Philippe Poizat, Ludovic Bellon and Pierre Verlot, submitted to Nature Nanotechnology

We report a new scanning thermomechanical microscopy platform enabling to both heat and acquire the fluctuations of mechanical nanostructures with nanometric resolution. We use this platform to image the nanomechanical noise response of a 40 nm diameter nanowire while scanning a localized heat source across its surface. We develop a thermal backaction model, which we use to demonstrate a close connection between the structure of the nanowire, its thermal response, its dissipation and its fluctuations. We notably identify the presence of a localized thermoelastic defect, which we demonstrate behaves as a single fluctuation hub, whose e-beam excitation yields a far off-equilibrium vibrational state, largely dominated by the quantum fluctuations of the heating source. Our platform is of interest for future development of ultra-low loss nanophononic devices, and appears as a new playground for investigating quantum thermodynamics in the strongly dissipative regime and at room temperature.

Aubin Archambault, Caroline Crauste-Thibierge, Sergio Ciliberto, Ludovic Bellon, submitted to EPL

We describe an experiment on an underdamped mechanical oscillator used as an information engine. The system is equivalent to an inertial Brownian particle confined in a harmonic potential whose center is controlled by a feedback protocol which measures the particle position at a specific sampling frequency 1/𝜏. Several feedback protocols are applied and the power generated by the engine is measured as a function of the oscillator parameters and the sampling frequency. The optimal parameters are then determined. The results are compared to the theoretical predictions and numerical simulations on overdamped systems. We highlight the specific effects of inertia, which can be used to increase the amount of power extracted by the engine. In the regime of large 𝜏, we show that the produced work has a tight bound determined by information theories.

Nicolas Barros, Sergio Ciliberto, Ludovic Bellon, submitted to Phys. Rev. Lett.

arXiv: 2402.18556

We demonstrate experimentally that, applying optimal protocols which drive the system between two equilibrium states characterized by a free energy difference ΔF, we can maximize the probability of performing the transition between the two states with a work W smaller than ΔF. The second law holds only on average, resulting in the inequality ⟨W⟩≥ΔF. The experiment is performed using an underdamped oscillator evolving in a double-well potential. We show that with a suitable choice of parameters the probability of obtaining trajectories with W≤ΔF can be larger than 90 %. Very fast protocols are a key feature to obtain these results which are explained in terms of the Jarzynski equality.

Alex Fontana and Ludovic Bellon, accepted for publication in Phys. Rev. App. (2024)

arXiv: 2402.04887
[dataset] doi: 10.5281/zenodo.11110783

Optical beam deflection is a popular method to measure the deformation of micro-mechanical devices. As it measures mostly a local slope, its sensitivity depends on the location and size of the optical spot. We present a method to evaluate precisely these parameters, using the relative amplitude of the thermal noise induced vibrations. With a case study of a micro-cantilever, we demonstrate the accuracy of the approach, as well as its ability to fully characterize the sensitivity of the detector, and the parameters (mass,
stiffness) of the resonator.