Ultra-low acoustoelectric attenuation in graphene

We investigate the acoustoelectric properties of graphene and extract its acoustoelectric attenuation Gamma as a function of the carrier density n, tuned via ionic liquid gating. Acoustoelectric effects in graphene are induced by launching surface acoustic waves (SAWs) on a piezoelectric LiNbO3 substrate. We measure the acoustoelectric current I-ae through graphene and extract the SAW attenuation factor Gamma as a function of n. The magnitude of I-ae increases with decreasing n when the n is far from the charge neutral point (CNP). When n is tuned across the CNP, I-ae first exhibits a local maximum, vanishes at the CNP, and then changes sign in accordance with the associated change in the carrier polarity. By contrast, Gamma monotonically increases with decreasing n and reaches a maximum at the CNP. The extracted values of Gamma, calibrated at the central frequency of 189 MHz, vary from 0.4m(-1) to 6.8m(-1), much smaller than the values for known two-dimensional systems. Data analysis suggests that the evolution of I-ae and Gamma with n manifests the electronic states of graphene. Our experimental findings provide insightful information for developing innovative graphene-based devices. Published by AIP Publishing.