Ahn, Kang-HunMohanty, Pritiraj2018-04-172018-04-172003-02-28Ahn, K. H., & Mohanty, P. (2003). Quantum friction of micromechanical resonators at low temperatures. Physical review letters, 90(8), 085504. doi: 10.1103/PhysRevLett.90.0855040031-9007https://hdl.handle.net/2144/28339Dissipation of micro- and nanoscale mechanical structures is dominated by quantum-mechanical tunneling of two-level defects intrinsically present in the system. We find that at high frequencies-usually, for smaller, micron-scale structures-a novel mechanism of phonon pumping of two-level defects gives rise to weakly temperature-dependent internal friction, Q-1, concomitant to the effects observed in recent experiments. Because of their size, comparable to or shorter than the emitted phonon wavelength, these structures suffer from superradiance-enhanced dissipation by the collective relaxation of a large number of two-level defects contained within the wavelength.085504 - ?©2003 American Physical SocietyScience & technologyPhysical sciencesPhysicsMechanical properties2-level systemsSiliconDissipationMesoscale and nanoscale physicsGeneral physicsArticle10.1103/PhysRevLett.90.085504