Santos-Cottin David, Casula Michele, Lantz Gabriel, Klein Yannick, Petaccia Luca, Le Fèvre Patrick, Bertran François, Papalazarou Evangelos, Marsi Marino, Gauzzi Andrea
IMPMC, Sorbonne Universités, Université Pierre et Marie Curie, CNRS, IRD, MNHN, 4 place Jussieu, 75252 Paris, France.
Laboratoire de Physique des Solides, CNRS, Université Paris-Sud, Université Paris-Saclay, 91405 Orsay, France.
Nat Commun. 2016 Apr 19;7:11258. doi: 10.1038/ncomms11258.
There has been increasing interest in materials where relativistic effects induce non-trivial electronic states with promise for spintronics applications. One example is the splitting of bands with opposite spin chirality produced by the Rashba spin-orbit coupling in asymmetric potentials. Sizable splittings have been hitherto obtained using either heavy elements, where this coupling is intrinsically strong, or large surface electric fields. Here by means of angular resolved photoemission spectroscopy and first-principles calculations, we give evidence of a large Rashba coupling of 0.25 eV Å, leading to a remarkable band splitting up to 0.15 eV with hidden spin-chiral polarization in centrosymmetric BaNiS2. This is explained by a huge staggered crystal field of 1.4 V Å(-1), produced by a gliding plane symmetry, that breaks inversion symmetry at the Ni site. This unexpected result in the absence of heavy elements demonstrates an effective mechanism of Rashba coupling amplification that may foster spin-orbit band engineering.
相对论效应诱导出具有自旋电子学应用前景的非平凡电子态的材料，已引发越来越多的关注。一个例子是在非对称势中，由 Rashba 自旋轨道耦合产生的具有相反自旋手性的能带分裂。迄今为止，通过使用重元素（这种耦合本质上很强）或大表面电场，已获得了可观的分裂。在这里，通过角分辨光电子能谱和第一性原理计算，我们证明了在中心对称的 BaNiS2 中存在 0.25 eV Å 的大 Rashba 耦合，导致高达 0.15 eV 的显著能带分裂，并伴有隐藏的自旋手性极化。这是由滑移面对称性产生的 1.4 V Å⁻¹ 的巨大交错晶体场所解释的，该场打破了 Ni 位点的反演对称性。在没有重元素的情况下出现的这一意外结果，展示了一种 Rashba 耦合放大的有效机制，这可能会促进自旋轨道能带工程的发展。
