  The recent observation of superconductivity at the interfaces between KTaO3
and EuO (or LaAlO3) offers a new example of emergent phenomena at oxide
interfaces. This superconductivity exhibits an unusual strong dependence on the
crystalline orientation of KTaO3 and its superconducting transition temperature
Tc is nearly one order of magnitude higher than that of the seminal
LaAlO3/SrTiO3 interface. To understand its mechanism, it is crucial to address
if the formation of oxide interfaces is indispensable for the presence of
superconductivity. Here, by exploiting ionic liquid (IL) gating, we obtain
superconductivity at KTaO3 (111) and (110) surfaces with Tc up to 2.0 K and 1.0
K, respectively. This oxide-interface-free superconductivity gives a clear
experimental evidence that the essential physics of KTaO3 interface
superconductivity lies in the KTaO3 surfaces doped with electrons. Moreover,
the ability to control superconductivity at surfaces with IL provides a simple
way to study the intrinsic superconductivity in KTaO3.
