强自旋轨道钙钛矿KTaO $_3$极性表面二维电子气的子带结构
Subband structure of a two-dimensional electron gas formed at the polar surface of the strong spin-orbit perovskite KTaO$_3$
摘要：
我们证明了在$5d$过渡金属氧化物KTaO $_3$的$(100)$表面形成二维电子气。从角分辨光电子能谱中，我们发现量子限域提升了体能带结构的轨道简并度，并导致了由轻、重载流子的子带态阶梯组成的2DEG。尽管有很强的自旋-轨道耦合，我们的测量提供了一个直接的上限为潜在的Rashba自旋分裂只有$Δ{k}_\parallel\sim\0.02$ $^{-1}$在费米能级。与非极性SrTiO $_3(100)$相比，KTaO $_3(100)$表面的极性性质似乎有助于介导2DEG的形成。
英文摘要：
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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