Gate Tunable Cooperativity between Vibrational Modes.

Coupling between a mechanical resonator and optical cavities, microwave resonators, or other mechanical resonators have been used to observe interesting effects from sideband cooling to coherent manipulation of phonons. Here we demonstrate strong coupling between different vibrational modes of MoS drum resonators at room temperature. We observe intermodal as well as intramodal coupling. Cooperativity, a measure of coupling between the two modes, can be tuned by more than an order of magnitude by changing the direct current gate bias. The large measured cooperativity of about 900 at room temperature indicates that the phonon population can be coherently transferred between the modes for more than 500 cycles. This coherent oscillation is of great interest in studying quantum effects in macroscopic objects.