Two-dimensional superconductivity at interfaces and surfaces of KTaO3

Nov. 30 10:25-10:50

*Yanwu Xie1
Zhejiang University (China)1

A new family of oxide-interface superconductors, with a transition temperature (Tc) up to 2.2 K, were recently found at interfaces between KTaO3 and other oxides (EuO or LaAlO3) [1-3]. In this talk, we will present our recent progresses in this system. We demonstrate that the superconductivity is sensitive to the orientation of KTaO3 and find a Tc ~1 K superconductivity at (110)-orientated interface [2]. We successfully tune the superconducting LaAlO3/KTaO3(111) interface by applying a gate bias across KTaO3[3]. By in-situ transport measurements during growth, we conclude that the formation mechanism of the LaAlO3/KTaO3 interface electron gas is the electron transfer from oxygen vacancies in LaAlO3 film to KTaO3 substrate [4]. By exploiting ionic liquid gating, we obtain superconductivity at bare KTaO3(111) and (110) surfaces with Tc values up to 2.0 K and 1.0 K, respectively [5], which are almost the same as that in the corresponding interfaces, suggesting that the essential physics of KTaO3 interface superconductivity lies in the KTaO3 surfaces doped with electrons.

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[2] Z. Chen, Z. Liu, Y. Sun, X. Chen, Y. Liu, H. Zhang, H. Li, M. Zhang, S. Hong, T. Ren, C. Zhang, H. Tian, Y. Zhou, J. Sun, and Y. Xie, Phys. Rev. Lett. 126, 026802, (2021).
[3] Z. Chen, Y. Liu, H. Zhang, Z. Liu, H. Tian, Y. Sun, M. Zhang, Y. Zhou, J. Sun, and Y. Xie, Science 372, 721,(2021).
[4] Y. Sun, Y. Liu, S. Hong, Z. Chen, M. Zhang, and Y. Xie, Phys. Rev. Lett. 127, 086804, (2021).
[5] T. Ren, M. Li, X. Sun, L. Ju, Y. Liu, S. Hong, Y. Sun, Q. Tao, Y. Zhou, Z. Xu, and Y. Xie, Sci. Adv. 8, eabn4273, (2022).

Keywords: KTaO3, interface superconductor, oxide interface , two-dimensional superconductivity