A Mott transistor with giant switching ratio at room temperature and its emulation of artificial synapses

Electric double layer transistors (EDLTs), capable of stably realizing large amounts of carrier modulation in aqueous environments and converting biochemical and biological inputs into amplified electronic signals, have emerged as fundamental building blocks in neuromorphic computing. Here, we present a three-terminal Mott synaptic device based on EDLTs, using a 5d spin-orbit coupling induced Mott insulator Sr₂IrO₄ (SIO) and ionic liquid (IL) as the channel material and gate dielectric, respectively. Based on these devices, a staged bidirectional variable resistance effect has been realized by simply applying an electric field. The on/off current ratios of the SIO-channel EDLTs are sensitive to measurement vacuum degree and a giant switching ratio of 10⁵ can be achieved at room temperature. No structural variation with gating voltage is found by the in situ X-ray diffraction analysis. The mechanism of the electric double layer (EDL) field effect formed by traditional ILs and enhanced EDL field effect by H₂O electrolysis is proposed. Furthermore, the multi-essential functions of the biological synapse are well emulated in our synaptic transistors due to the electric-field-controlled bidirectional conductivity modulation and multi-resistance states. These results provide insight into the potential application of the Mott insulators with strong spin-orbital coupling for designing future artificial synapses.