Experimental Evidence of Cubic Rashba Effect in an Inversion-Symmetric Oxide

We present evidence of cubic Rashba spin splitting in a quasi-two-dimensional electron gas formed at a surface of (001) SrTiO3 single crystal from the weak localization or antilocalization (WAL) analysis of the low-temperature magnetoresistance. Our WAL data were well fitted by the model assuming m(j) = +/- 3/2 for the spin-split pair, in which 2 pi rotation of the electron wave vector k(parallel to) in the k(x)-k(y) plane accompanies 6 pi rotation of the spin quantization axis. This finding pertains to the p symmetry of the t(2g) electronic band derived from d electrons in SrTiO3, which provides insights into the surface electronic state of (001) SrTiO3.