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A new light on nanomechanical dissipation

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Researchers from laboratory Matériaux et Phénomènes Quantiques have shown that crystalline nanomechanical resonators are affected by surface fluctuation mechanisms that are ubiquitous in condensed matter.

High-Q nanomechanical resonators are becoming central with the development of quantum optomechanics and nanomechanical sensing. Despite this chief position in modern physics, we still lack an exact understanding of their dissipation mechanisms, which remain subject to speculation and debate. The paper "Microscopic nanomechanical dissipation in gallium arsenide resonators" is a careful experimental and theoretical study that brings answers to open questions in this field.

The investigation is carried on state-of-the-art crystalline nanoresonators, which are generally perceived as best candidates for applications. Thanks to nanofabrication control and modeling of phonon-phonon interactions, the work disentangles loss channels affecting these nano-systems, finally pinpointing the importance of surface dissipation. The latter is shown to originate from fluctuating two-level systems (TLS), mainly localized at surfaces, which appear to be the dominating source of noise and loss.

Hence crystalline nanomechanical devices, just like superconducting qu-bits and resonators, are finally governed by fluctuations mechanisms that are ubiquitous in condensed matter. These mechanisms could be quenched at ultra-low temperature and with improved surfaces.

Figure :
A nanomechanical resonator. The fluctuating Two-Level Systems (TLS) localized at the surfaces dissipate the mechanical energy of vibration.

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Reference :
Microscopic nanomechanical dissipation in gallium arsenide resonators, M. Hamoumi, P. E. Allain, W. Hease, E. Gil-Santos, L. Morgenroth, B. Gérard, A. Lemaître, G. Leo, and I. Favero, Phys. Rev. Lett. 120, 223601 (2018)