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arXiv · 1111.2782

Subband structure of a two-dimensional electron gas formed at the polar surface of the strong spin-orbit perovskite KTaO$_3$

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. Hussain·Y. Tokura·Z. -X. Shen·H. Y. Hwang·F. Baumberger·W. Meevasana
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Abstract

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 $Δ{k}_\parallel\sim\0.02$ Å$^{-1}$ 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$_3(100)$.

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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. Hussain, Y. Tokura, Z. -X. Shen, H. Y. Hwang, F. Baumberger, W. Meevasana. 2011-11-11. Subband structure of a two-dimensional electron gas formed at the polar surface of the strong spin-orbit perovskite KTaO$_3$. https://doi.org/10.1103/physrevlett.108.117602

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