Surface acoustic wave amplification in narrow graphene nanoribbons under a dc electric field

The paper analyzes the amplification of surface acoustic waves (SAWs) in narrow graphene nanoribbons (GNRs) under the action of a dc electric field, which causes the drift of free charge carriers in the direction of SAW propagation at a speed exceeding the speed of SAWs in GNRs. We predict large periodic oscillations in the SAW gain with the variation of the electron concentration in the GNR, controlled by the gate voltage applied to the GNR sample. The amplification of SAWs at the oscillation maxima can reach values of several tens of dB/cm in the gigahertz frequency range at room temperature and a fairly moderate dc electric field strength of about 300 V/cm.