Two-dimensional superconductivity at the surfaces of KTaO3 gated with ionic liquid

TL;DR

This study demonstrates two-dimensional superconductivity on KTaO3 surfaces via ionic liquid gating, showing that superconductivity can be achieved without oxide interfaces and is intrinsic to the doped surfaces.

Contribution

It provides experimental evidence that superconductivity in KTaO3 is intrinsic to its surfaces doped with electrons, independent of oxide interface formation.

Findings

Superconductivity observed at KTaO3 (111) and (110) surfaces with Tc up to 2.0 K and 1.0 K.

Superconductivity can be induced without oxide interfaces using ionic liquid gating.

Surface doping is sufficient to produce superconductivity in KTaO3.

Abstract

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.