A spin–orbit scattering–enhanced high upper critical field at the LaAlO3/KTaO3(111) superconducting interface

Abstract

Spin–orbit interaction is essential to enhance the in-plane upper critical field of two-dimensional superconductors. Here, we report the LaAlO _3 /KTaO _3 (111) superconducting interface ( T _c,0 ≈ 0.475 K) with a high in-plane upper critical field (∼1.6 T), which is approximately 1.8 times the Pauli paramagnetic limit. The H $ - $ T superconducting phase diagram is well-fitted by the Klemm–Luther–Beasley (KLB) theory, and the relevant spin–orbit scattering (SOS) length is approximately 32 nm. Furthermore, normal-state magnetotransport measurements show signatures of weak antilocalization caused by strong spin–orbit coupling in LaAlO _3 /KTaO _3 (111). The spin diffusion length derived from magnetotransport measurements was 40 nm at 2 K, which is comparable with the SOS length. The conformity of the phase diagram with the KLB theory and the consistency of normal state spin diffusion length and superconducting SOS length indicate that the high in-plane upper critical field at the LaAlO _3 /KTaO _3 (111) superconducting interface is enhanced by SOS.

Keywords

• superconductors
• LaAlO3/KTaO3 (111)
• spin-orbit scattering
• Pauli paramagnetic limit