"Subband Structure of a Two-Dimensional Electron Gas Formed at the Polar Surface of the Strong Spin-Orbit Perovskite KTaO3"

King, P. D. C.: He, R. H., Eknapakul, T., Buaphet, P., Mo, S. K., Kaneko, Y., Harashima, S., Hikita, Y., Bahramy, M. S., Bell, C., Hussain, Z., Tokura, Y., Shen, Z. X., Hwang, H. Y., Baumberger, F., Meevasana, W.; Physical Review Letters, 03/14/12.

Additional Authors: He, R. H., Eknapakul, T., Buaphet, P., Mo, S. K., Kaneko, Y., Harashima, S., Hikita, Y., Bahramy, M. S., Bell, C., Hussain, Z., Tokura, Y., Shen, Z. X., Hwang, H. Y., Baumberger, F., Meevasana, W.

Abstract:

We demonstrate the formation of a two-dimensional electron gas (2DEG) at the (100) surface of the 5d transition-metal oxide KTaO3. 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 the potential Rashba spin splitting of only Δk∼0.02  Å-1 at the Fermi level. The polar nature of the KTaO3(100) surface appears to help mediate the formation of the 2DEG as compared to nonpolar SrTiO3(100).