Tunable and Reconfigurable Frequency Comb in Atomically Thin Nanomechanical Resonator Via Low-frequency Pumping

We demonstrate the generation of a fixed-spacing phononic frequency comb in a graphene nanomechanical resonator via internal resonance. Its dynamic behavior is subsequently tuned by using a low-frequency pump. The device is characterized by multi-modal resonance measurements to identify the internal resonance regime. By applying a gate voltage and a single-tone excitation around fundamental mode, a phononic frequency comb with a tooth spacing of 0.38 MHz is generated. Subsequently, we apply a low-frequency single pump excitation on device to modulate its effective stiffness, enabling control over both the comb spacing and the number of spectral lines. Within this tuning range, we observe multifaceted frequency comb dynamics. These include combs with non-uniform spacing, which consist of multiple miniature combs, as well as equally spaced combs generated by the direct mixing of the pump and drive signals. This methodology for on-chip comb generation and dynamic manipulation paves the way for highly tunable frequency combs, precise frequency control in nanomechanical systems ((NEMS), and high-precision measurement/sensing.