Collective dynamics of capacitively coupled oscillators based on NbO2 memristors

The dynamics of NbO2-based single and coupled oscillators are comprehensively investigated in this study. For single oscillators, the oscillation frequency is shown to have a strong dependence on the source voltage and load resistance. The range of the frequency modulation can be tuned from 2.1 to 6.8 MHz, while the load resistance is fixed at 3 kΩ. For coupled oscillators, rich and complex dynamics including in- and antiphase locking phenomena are carefully explored by using a mutual capacitor. According to different phase trajectories on the phase plane of both voltages across two devices, the evolution of the source voltage vs coupling capacitance phase diagram is shown with load resistance mismatch. Four coupling regions in the phase diagram are recognized, including a butterfly-shaped coupling zone, a linear coupling zone, a transition zone, and an uncoupled zone. As the load resistance mismatch increases from 1.0% to 3.9%, the linear coupling zone gradually disappears while the butterfly-shaped coupling zone gradually expands. When the load resistance mismatch is larger than 9.5%, the butterfly-shaped coupling zone gradually decreases while the uncoupled zone enlarges significantly.