Two-dimensional superconductivity at the surfaces of KTaO(3) gated with ionic liquid

The recent discovery of superconductivity at the interfaces between KTaO(3) and EuO (or LaAlO(3)) gives birth to the second generation of oxide interface superconductors. This superconductivity exhibits a strong dependence on the surface plane of KTaO(3), in contrast to the seminal LaAlO(3)/SrTiO(3) interface, and the superconducting transition temperature T(c) is enhanced by one order of magnitude. For understanding its nature, a crucial issue arises: Is the formation of oxide interfaces indispensable for the occurrence of superconductivity? Exploiting ionic liquid (IL) gating, we are successful in achieving superconductivity at KTaO(3)(111) and KTaO(3)(110) surfaces with T(c) up to 2.0 and 1.0 K, respectively. This oxide-IL interface superconductivity provides a clear evidence that the essential physics of KTaO(3) interface superconductivity lies in the KTaO(3) surfaces doped with electrons. Moreover, the controllability with IL technique paves the way for studying the intrinsic superconductivity in KTaO(3).