Anomalous temperature dependence of spin-orbit coupling in Al2O3/SrTiO3and Al2O3/KTaO3heterostructures.

Perovskite oxide-based heterostructures exhibit a range of exotic physical properties such as two-dimensional superconductivity, interface magnetism, tunable Kondo effect, and tunable spin-orbit coupling. Here, the magnetotransport properties of Al2O3/SrTiO3and Al2O3/KTaO3heterostructures are studied. Both Kondo effect and spin-orbit coupling-induced weak antilocalization (WAL) effect are observed at low temperatures. By analyzing the WAL curves, the spin relaxation time is extracted. Surprisingly, the extracted spin relaxation time unexpectedly decreases on increasing temperature in all samples. This indicates that the strength of the spin-orbit coupling is progressively enhanced on increasing temperature, conflicting with theoretical prediction. This anomalous temperature dependence is explained by the interplay between the Kondo effect and the D'yakonov-Perel spin relaxation mechanism.