Dimensionality-tuned electronic structure of nickelate superlattices explored by soft-x-ray angle-resolved photoelectron spectroscopy
Dimensionality-tuned electronic structure of nickelate superlattices explored by soft-x-ray angle-resolved photoelectron spectroscopy
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DOI：
10.1103/physrevb.92.125130
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发表时间：
2015-09-16
影响因子：
3.7
通讯作者：
Claessen, R.
中科院分区：
文献类型：
--
作者：
Berner, G.;Sing, M.;Claessen, R.
外延 LaNiO3/LaAlO3 超晶格的电子和磁性特性可以通过层厚度和衬底引起的应变来调节。在这里，我们报告了通过软 X 射线光电发射在压缩应变下对超晶格中埋入镍盐层的 k 空间分辨电子结构的直接测量。在解开光电子衍射引起的角度相关信号的强外在贡献之后，我们能够从数据中提取费米表面信息。我们发现，随着 LaNiO3 厚度减小到两个晶胞 (2 uc)，准粒子相干性会大大降低，这与输运测量中看到的尺寸引起的金属到绝缘体的转变一致。尽管如此，在强烈不相干的背景之上，可以在 2 uc 超晶格中识别出残留的费米面，其嵌套特性与最近报道的自旋密度波 (SDW) 不稳定性一致。 Ni 3d 谱的整体行为和不存在完全能隙打开表明 SDW 相由强有序参数波动主导。
The electronic and magnetic properties of epitaxial LaNiO3/LaAlO3 superlattices can be tuned by layer thickness and substrate-induced strain. Here, we report on direct measurements of the k-space-resolved electronic structure of buried nickelate layers in superlattices under compressive strain by soft-x-ray photoemission. After disentangling strong extrinsic contributions to the angle-dependent signal caused by photoelectron diffraction, we are able to extract Fermi surface information from our data. We find that with decreasing LaNiO3 thickness down to two unit cells (2 uc) quasiparticle coherence becomes strongly reduced, in accord with the dimension-induced metal-to-insulator transition seen in transport measurements. Nonetheless, on top of a strongly incoherent background a residual Fermi surface can be identified in the 2 uc superlattice whose nesting properties are consistent with the spin-density-wave (SDW) instability recently reported. The overall behavior of the Ni 3d spectra and the absence of a complete gap opening indicate that the SDW phase is dominated by strong order parameter fluctuations.