Surface termination conversion effect on the electronic structure of two-dimensional electron gas at EuTiO 3 surfaces

We perform $\mathit{in} \mathit{situ}$ angle-resolved photoemission spectroscopy to investigate the effect of surface termination conversion on two-dimensional electron gas (2DEG) at the ${\mathrm{EuTiO}}_{3}$(001) surface. We successfully engineered ${\mathrm{EuTiO}}_{3}$ with nearly single ${\mathrm{TiO}}_{2}$ termination via epitaxial growth on ${\mathrm{TiO}}_{2}$-terminated ${\mathrm{SrTiO}}_{3}$, and ${\mathrm{EuTiO}}_{3}$ with nearly complete EuO termination by inserting a ${\mathrm{SrRuO}}_{3}$ buffer layer into the heterostructure. The orbital configuration of the 2DEG exhibits a strong dependence on the ${\mathrm{EuTiO}}_{3}$ termination, and this experimental observation matches our first-principles calculation results very well. Furthermore, we observe the termination dependence of a kink feature in ${d}_{xy}$ band. This finding implies that many-body interactions, and possibly magnetism, are influenced by the surface termination. Our study not only introduces a method to fabricate surface or interfacial 2DEG system, but also highlights the effect of termination conversion on magnetic 2DEG.