Catégorie : Article

Aubin Archambault, Caroline Crauste-Thibierge and Ludovic Bellon, J. Appl. Phys. 135, 094502 (2024)

Article: doi: 10.1063/5.0189480
Dataset:  doi: 10.5281/zenodo.10102664
Software : doi: 10.5281/zenodo.10103601

Colloidal probes are often used in force microscopy when the geometry of the tip-sample interaction should be well controlled. Their calibration requires the understanding of their mechanical response, which is very sensitive to the details of the force sensor consisting of a cantilever and the attached colloid. We present analytical models to describe the dynamics of the cantilever and its load positioned anywhere along its length. The thermal noise calibration of such probes is then studied from a practical point of view, leading to correction coefficients that can be applied in standard force microscope calibration routines. Experimental measurements of resonance frequencies and thermal noise profiles of raw and loaded cantilevers demonstrate the validity of the approach.

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A.-H. Chen, C.P. Dempsey, M. Pendharkar, A. Sharma, B. Zhang, S. Tan, L. Bellon, S.M. Frolov, C.J. Palmstrom, E. Bellet-Amalric, and M. Hocevar, Nanotechnology 35 075702

[Article] doi: 10.1088/1361-6528/ad079e
[Data set] doi: 10.5281/zenodo.7581136

Metal deposition with cryogenic cooling is a common technique in the condensed matter community for producing ultra-thin epitaxial superconducting layers on semiconductors. However, a significant challenge arises when these films return to room temperature, as they tend to undergo dewetting. This issue can be mitigated by capping the films with an amorphous layer. In this study, we investigate the influence of different in situ fabricated caps on the structural characteristics of Sn thin films deposited at 80 K on InSb substrates. Regardless of the type of capping, we consistently observe that the films remain smooth upon returning to room temperature and exhibit epitaxy on InSb in the cubic Sn (α-Sn) phase. Notably, we identify a correlation between alumina capping using an electron beam evaporator and an increased presence of tetragonal Sn (β-Sn) grains. This suggests that heating from the alumina source may induce a partial phase transition in the Sn layer. The existence of the β-Sn phase induces superconducting behavior of the films by percolation effect. This study highlights the potential for tailoring the structural properties of cryogenic Sn thin films through in situ capping. This development opens avenues for precise control in the production of superconducting Sn films, facilitating their integration into quantum computing platforms.

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Salambô Dago, Sergio Ciliberto, Ludovic Bellon, Adv. Phys. Res. 2023 2300074 (2023)

[Article] doi: 10.1002/apxr.202300074
[Dataset] doi: 10.5281/zenodo.8307734

The reliability of fast repeated erasures is studied experimentally and theoretically in a 1-bit underdamped memory. The bit is encoded by the position of a micro-mechanical oscillator whose motion is confined in a double well potential. To contain the energetic cost of fast erasures, we use a resonator with high quality factor Q: the erasure work W is close to Landauer’s bound, even at high speed. The drawback is the rise of the system’s temperature T due to a weak coupling to the environment. Repeated erasures without letting the memory thermalize between operations result in a continuous warming, potentially leading to a thermal noise overcoming the barrier between the potential wells. In such case, the reset operation can fail to reach the targeted logical state. The reliability is characterized by the success rate R^s_i after i successive operations. W, T and R^s_i are studied experimentally as a function of the erasure speed. Above a velocity threshold, T soars while R^s_i collapses: the reliability of too fast erasures is low. These experimental results are fully justified by two complementary models. We demonstrate that Q≃10 is optimal to contain energetic costs and maintain high reliability standards for repeated erasures at any speed.

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Basile Pottier, Carlos Plata, Emmanuel Trizac, David Guéry-Odelin and Ludovic Bellon, Phys. Rev. Applied  19, 034072 (2023)

[Article] doi: 10.1103/PhysRevApplied.19.034072
[Data set] doi: 10.5281/zenodo.7669037

In most systems, thermal diffusion is intrinsically slow with respect to mechanical relaxation. We devise here a generic approach to accelerate the relaxation of the temperature field of a 1D object, in order to beat the mechanical time scales. This approach is applied to a micro-meter sized silicon cantilever, locally heated by a laser beam. A tailored driving protocol for the laser power is derived to reach arbitrarily fast the thermal stationary state. The model is implemented experimentally yielding a significant acceleration of the thermal relaxation, up to a factor 30. An excellent agreement with the theoretical predictions is reported. This strategy allows to reach a thermal steady state significantly faster than the natural mechanical relaxation.

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Alex Fontana and Ludovic Bellon, Physics. Rev. E 107, 034118 (2023)

[Article] doi: 10.1103/PhysRevE.107.034118
[Data set] doi: 10.5281/zenodo.7640707

For systems in equilibrium at a temperature T, thermal noise and energy damping are related to T through the fluctuation-dissipation theorem (FDT). We study here an extension of the FDT to an out-of-equilibrium steady state: a microcantilever subject to a constant heat flux. The resulting thermal profile in this spatially extended system interplays with the local energy dissipation field to prescribe the amplitude of mechanical fluctuations. Using three samples with different damping profiles (localized or distributed), we probe this approach and experimentally demonstrate the link between fluctuations and dissipation. The thermal noise can therefore be predicted a priori from the measurement of the dissipation as a function of the maximum temperature of the micro-oscillator.

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Baptiste Ferrero and Ludovic Bellon, EPL 139, 55002 (2022)

[Article] doi: 10.1209/0295-5075/ac8761
[Data set] doi:10.5281/zenodo.6801118

The two output signals of quadrature phase interferometers allow to benefit both from the high sensitivity of interferometry (working inside a fringe) and from an extended input range (counting fringes). Their calibration to reach a linear output is traditionally performed using Heydemann’s correction, which involves fitting one output versus the other by an ellipse. Here we present two alternative methods based on the linear response of the measurement to a sinusoidal input in time, which enables a direct calibration with an excellent linearity. A ten fold improvement with respect to the usual technique is demonstrated on an optical interferometer measuring the deflection of scanning force microscopy cantilevers.

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Salambô Dago, Jorge Pereda, Sergio Ciliberto and Ludovic Bellon, J. Stat. Mech. 2022, 053209 (2022)

[Article] doi: 10.1088/1742-5468/ac6d62
[Erratum] doi: 10.1088/1742-5468/acd697
[Dataset] doi: 10.5281/zenodo.6497247

Virtual potentials are a very elegant, precise and flexible tool to manipulate small systems and explore fundamental questions in stochastic thermodynamics. In particular double-well potentials have applications in information processing, such as the demonstration of Landauer’s principle. Nevertheless, virtual double-well potentials had never been implemented in underdamped systems. In this article, we detail how to face the experimental challenge of creating a feedback loop for an underdamped system (evolving at much smaller time scale than its overdamped counterpart), in order to build a tunable virtual double-well potential. To properly describe the system behavior in the feedback trap, we express the commutation time in the double-well for all barrier heights, combining for the first time  Kramer’s description, valid at high barriers, with an adjusted model for lower ones. We show that a small hysteresis or delay of the feedback loop in the commutation between the two wells results in a modified velocity distribution, interpreted as a cooling of the kinetic temperature of the system. We successfully address all issues to create experimentally a virtual potential that is statistically indistinguishable from a physical one, with a tunable barrier height and energy step between the two wells.

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