Fig. 1: Device geometry and transport behavior of AlO_x/KTaO₃ (111) interface.

a In a pure ionic picture, (111) oriented KTaO₃ can be considered as a sequence of alternating [KO₃]⁵⁻ and Ta⁵⁺ planes. Arrangement of Ta⁺⁵ ions in two adjacent (111) planes are labeled by Ta-I and Ta-II⁶⁹. b Schematics of two Hall bars made on a AlO_x/KTaO₃ (111) heterostructure. The width of the Hall bar is 476 μm and 445 μm for [\(11\bar{2}\)] and [\(1\bar{1}0\)] directions, respectively and the length between the voltage probes is 1.87 mm for both the Hall bars. c Temperature-dependent R_S for both the Hall bars for a 7 nm AlO_x/KTaO₃ (111) sample. Inset shows a magnified view around the superconducting transition temperature. The normal state R_S (T) shows a non Fermi liquid behavior (R_S ∝ T^α where α < 2) in a broad range of temperatures from 75 K to 300 K with α = 1.5 and 1.3 for current along [\(11\bar{2}\)] and [\(1\bar{1}0\)], respectively. This behavior is in sharp contrast with the T³ behavior observed in bulk electron doped KTaO₃, where no superconductivity has been observed (see Supplementary Fig. 2). Low temperature variation of R_S under B_⊥ has been shown in d (from 0 T to 0.1 T) and e (from 0.2 T to 9 T) for the Hall bar along [\(11\bar{2}\)]. Dotted lines in e show logarithmic dependence of R_S with the temperature near the avoided superconductor insulator transition.