Theory of ultrafast conductance modulation in electrochemical protonic synapses by multiphase polarization

Recent advances in protonic electrochemical random-access memory (ECRAM) have demonstrated ultrafast, nanosecond switching dynamics, seemingly faster than diffusion. We develop a theory to explain how these devices outperform some counterparts by up to five orders of magnitude by leveraging multiphase polarization in tungsten oxide, which can be tuned during annealing of the material. Supported by simulations, the theory shows that high-concentration metallic phases formed electrochemically along the gate enable the conductance to be modulated linearly and symmetrically throughout the ultrafast switching protocols.