XAS Study of inversion and time-reversal symmetry breaking in KTaO3 based 2D-electron gases

Recently, the novel oxide 2D-electron gases (2DEGs) discovered interfaces between quantum paraelectric KTaO3 and band insulating oxides attracted wide-spread interest due to the interplay between the large spin-orbit coupling of Ta-5d states and the superconductivity. Very surprisingly, these 2DEGs show very weak superconductivity at the (001) interface (Tc<50 mK), but robust Tc of 2.2K and 1.1 K at the (111) and (110) interfaces, respectively. Here, we propose polarization dependent Ta-NIII (Ta 4p->5d) [4] and O-K (O 1s->2p) [5] edges x-ray absorption spectroscopy (XAS) to establish the Ta-5d crystal-field symmetry and t2g splitting, and their relationship with the ground states in the 2DEGs formed at the (001), (110) and (111) interfaces between KTO, non-magnetic (LaAlO3, AlOx) and ferromagnetic (EuO) overlayers. In EuO/KTO 2DEGs, we will also study magnetic correlation between Eu and Ta magnetic moments, by Eu-M4,5, Ta-NIII, and O-K edges x-ray magnetic circular dichroism (XMCD).