Subband structure of a two-dimensional electron gas formed at the polar   surface of the strong spin-orbit perovskite KTaO$_3$
  We demonstrate the formation of a two-dimensional electron gas (2DEG) at the $(100)$ surface of the $5d$ transition-metal oxide KTaO$_3$. From angle-resolved photoemission, we find that quantum confinement lifts the orbital degeneracy of the bulk band structure and leads to a 2DEG composed of ladders of subband states of both light and heavy carriers. Despite the strong spin-orbit coupling, our measurements provide a direct upper bound for potential Rashba spin splitting of only $\Delta{k}_\parallel\sim\0.02$ \AA$^{-1}$ at the Fermi level. The polar nature of the KTaO$_3(100)$ surface appears to help mediate formation of the 2DEG as compared to non-polar SrTiO$_3(100)$. 
P.D.C. King, R.H. He, T. Eknapakul, P. Buaphet, S.-K. Mo, Y. Kaneko,   S. Harashima, Y. Hikita, M.S. Bahramy, C. Bell, Z. Hu...
cond-mat.str-el cond-mat.mes-hall cond-mat.mtrl-sci