Clarendon Laboratory, University of Oxford, Oxford, OX1 3PU, UK.
Niels Bohr Institute, University of Copenhagen, 2100, Copenhagen, Denmark.
Nat Commun. 2023 May 24;14(1):2984. doi: 10.1038/s41467-023-38760-7.
Visualizing atomic-orbital degrees of freedom is a frontier challenge in scanned microscopy. Some types of orbital order are virtually imperceptible to normal scattering techniques because they do not reduce the overall crystal lattice symmetry. A good example is d/d (π,π) orbital order in tetragonal lattices. For enhanced detectability, here we consider the quasiparticle scattering interference (QPI) signature of such (π,π) orbital order in both normal and superconducting phases. The theory reveals that sublattice-specific QPI signatures generated by the orbital order should emerge strongly in the superconducting phase. Sublattice-resolved QPI visualization in superconducting CeCoIn then reveals two orthogonal QPI patterns at lattice-substitutional impurity atoms. We analyze the energy dependence of these two orthogonal QPI patterns and find the intensity peaked near E = 0, as predicted when such (π,π) orbital order is intertwined with d-wave superconductivity. Sublattice-resolved superconductive QPI techniques thus represent a new approach for study of hidden orbital order.
可视化原子轨道自由度是扫描显微镜学的前沿挑战。某些类型的轨道有序对于普通散射技术来说几乎不可察觉，因为它们不会降低整体晶格对称性。一个很好的例子是四方晶格中的 d/d(π,π)轨道有序。为了提高检测能力，我们在这里考虑了超导相与正常相中的这种(π,π)轨道有序的准粒子散射干涉(QPI)特征。该理论表明，轨道有序产生的亚晶格特定 QPI 特征应该在超导相中强烈出现。在超导 CeCoIn 中的亚晶格分辨 QPI 可视化显示了晶格替代杂质原子处的两个正交 QPI 模式。我们分析了这两个正交 QPI 模式的能量依赖性，并发现了在 E = 0 附近强度峰值的情况，这与 d 波超导性交织的这种(π,π)轨道有序的预测一致。因此，亚晶格分辨超导 QPI 技术代表了研究隐藏轨道有序的新方法。
