通过角分辨光电子能谱检测的LaOBiS2多型体的预测电子标记
Predicted electronic markers for polytypes of LaOBiS2 examined via angular resolved photoemission spectroscopy
摘要：
在层状化合物中，非等效平面的自然周期性堆叠可以导致天然超晶格的形成;尽管在总能量上接近（因此在其热力学稳定性上），这种多型超晶格可以表现出不同的结构对称性，因此具有明显不同的电子性质，这些性质可以反过来用作“结构标记”。我们说明了这一一般原则上的层状LaOBiS 2化合物的密度泛函理论（DFT）计算（BiS 2）/（LaO）/（BiS 2）多型超晶格揭示定性和定量不同的电子结构标记与Rashba物理，但总能量只有~ 0.1 meV分开。这开启了通过电子标记识别细微结构特征的令人兴奋的可能性。我们发现，在不同的多型体的不同形式的对称性破缺的带简并的去除模式导致新的Rashba的“迷你间隙”与特征Rashba参数，可以从光谱学确定，从而缩小了物理上可能的多型体。通过识别这些不同的DFT预测的指纹，通过对LaBiOS 2的ARPES测量，我们发现了占主导地位的多型与少量的其他多型的混合物。这一结论，与中子散射的结果一致，建立ARPES检测理论上建立的电子标记作为一个强大的工具来描绘大力quasidegenerate多型体。
英文摘要：
The natural periodic stacking of symmetry-inequivalent planes in layered compounds can lead to the formation of natural superlattices; albeit close in total energy, (thus in their thermodynamic stability), such polytype superlattices can exhibit different structural symmetries, thus have markedly different electronic properties which can in turn be used as "structural markers". We illustrate this general principle on the layered LaOBiS2 compound where density-functional theory (DFT) calculations on the (BiS2)/(LaO)/(BiS2) polytype superlattices reveal both qualitatively and quantitatively distinct electronic structure markers associated with the Rashba physics, yet the total energies are only ~ 0.1 meV apart. This opens the exciting possibility of identifying subtle structural features via electronic markers. We show that the pattern of removal of band degeneracies in different polytypes by the different forms of symmetry breaking leads to new Rashba "mini gaps" with characteristic Rashba parameters that can be determined from spectroscopy, thereby narrowing down the physically possible polytypes. By identifying these distinct DFT-predicted fingerprints via ARPES measurements on LaBiOS2 we found the dominant polytype with small amounts of mixtures of other polytypes. This conclusion, consistent with neutron scattering results, establishes ARPES detection of theoretically established electronic markers as a powerful tool to delineate energetically quasidegenerate polytypes.
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