Dissipation in nanomechanical resonators at low temperatures

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• Dr. Andrew Armour, University of Nottingham
• Friday 30 April 2010, 14:00-15:00
• Physics East 217.

If you have a question about this talk, please contact Elizabeth Blackburn.

Nanomechanical resonators with frequencies ranging from a few MHz up to 1 GHz have important potential applications as ultra-sensitive force sensors Furthermore, when cooled to sufficiently low temperatures, nanomechanical resonators are expected to display quantum coherence. An understanding of dissipation in nanomechanical resonators is important for optimizing device applications and, more generally, it is an important prerequisite for developing appropriate models of environmental decoherence in such systems. However, despite significant experimental and theoretical efforts a full picture of the mechanisms that control the Quality factor of nanomechanical resonators has yet to be established, especially at low temperatures. In this talk I will review recent work in this area as well as presenting the results of our study [1] of dissipation in polycrystalline gold nanomechanical resonators cooled down to 10 mK. Measurements on beams with frequencies 7.95 MHz and 3.87 MHz revealed that from 30 mK to 500 mK the dissipation increases with temperature as T^0.5, with saturation occurring at higher temperatures. The relative frequency shift of the resonators increases logarithmically with temperature up to at least 400 mK. Similarities with the behaviour of bulk amorphous solids suggest that the dissipation in our resonators is dominated by two-level systems.

[1] A. Venkatesan, K. J. Lulla, M. J. Patton, A. D. Armour, C. J. Mellor and J. R. Owers-Bradley, Phys. Rev. B 81 , 073410 (2010).

This talk is part of the Condensed Matter Physics Seminars series.

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