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

Tianshuang Ren; Miaocong Li; Xikang Sun; Lele Ju; Yuan Liu; Siyuan Hong; Yanqiu Sun; Qian Tao; Yi Zhou; Zhu-An Xu; Yanwu Xie

doi:10.1126/sciadv.abn4273

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

Sci Adv. 2022 Jun 3;8(22):eabn4273. doi: 10.1126/sciadv.abn4273. Epub 2022 Jun 3.

Authors

Tianshuang Ren¹, Miaocong Li¹, Xikang Sun¹, Lele Ju¹, Yuan Liu¹, Siyuan Hong¹, Yanqiu Sun¹, Qian Tao¹, Yi Zhou^{2

3

4}, Zhu-An Xu^{1

5}, Yanwu Xie^{1

5}

Affiliations

¹ Interdisciplinary Center for Quantum Information, State Key Laboratory of Modern Optical Instrumentation, and Zhejiang Province Key Laboratory of Quantum Technology and Device, Department of Physics, Zhejiang University, Hangzhou 310027, China.
² Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
³ Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China.
⁴ Kavli Institute for Theoretical Sciences, CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing 100190, China.
⁵ Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China.

Abstract

The recent discovery of superconductivity at the interfaces between KTaO₃ and EuO (or LaAlO₃) gives birth to the second generation of oxide interface superconductors. This superconductivity exhibits a strong dependence on the surface plane of KTaO₃, in contrast to the seminal LaAlO₃/SrTiO₃ 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 KTaO₃(111) and KTaO₃(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 KTaO₃ interface superconductivity lies in the KTaO₃ surfaces doped with electrons. Moreover, the controllability with IL technique paves the way for studying the intrinsic superconductivity in KTaO₃.