Standing acoustic waves imaged by a nanomechanical resonator

Abstract

A nanomechanical beam resonator is used to image the standing wave pattern formed by two counter propagating surface acoustic waves of the Rayleigh type. As the intrinsic properties of the resonator are affected by a fast off-resonant mechanical excitation, it is possible to scan the wave pattern when shifting the positions of the wave's knots through the resonator's position. Due to the small size of the beam the wave is hardly disturbed by the nanoresonator, and the observed shifts in the resonator's eigenfrequency follow the expected form of a standing wave. At high acoustic amplitudes deviation from the linear behavior is observed while the dependence of the effect on the beam's magneto-impedance probe power elucidates the physical origin of the resonator tuning.