Changing carrier density is one of the most remarkable but common aspects of unconventional superconductors.Both for understanding the mechanism of exotic superconductivity and for novel technological applications,this“semiconductor-like”property plays a crucial role.Usually,this can be achieved by chemical substitution.However,in the chemical substitution tech-nique,the substitution is possible only within the realizable crystal structure,and the maximum amount of carrier density is limited to 1021 cm-3.Chemical substitution also introduces disorder,which often hinders extracting intrinsic aspects from the measured results.Therefore,different methods of carrier doping were consid-ered,such as doping by the electric field.In 2008,superconductiv-ity by electric field doping was realized in SrTiO3,using electric double layer transistor(EDLT)structure with ionic liquid gating(ILG)[1].Remarkable thing is that the density of doped carrier is 1015 cm-2(1022 cm-3).Since then,this technique was applied for many other superconductors,including high-Tc cuprate[2].The ILG also has a merit to realize a very clean and thin two-dimen-sional platform of superconductivity,which casts a question of the so far believed understanding of superconductor-insulator transition[3].Thus,the EDLT doped superconductivity has attracted growing interests in the modern research of superconductivity.