Voltage switching of a VO$_2$ memory metasurface using ionic gel

We have demonstrated large area, low voltage, non-volatile tuning of an electrolyte-based vanadium dioxide (VO$_2$) THz memory metasurface. Using ionic gel gating, voltage is applied to drive the insulator-to-metal transition in an underlying VO$_2$ layer. Through application of positive and negative voltages, the metasurface resonance can be switched into the ``off'' or ``on'' state by driving VO$_2$ into a more conductive or insulating regime, respectively. As compared to our graphene-based control devices, the longer saturation time of resonance modification in VO$_2$-based devices suggests that this voltage-induced switching originates primarily from electrochemical effects resulting from oxygen migration across the electrolyte-VO$_2$ interface.