近日，瑞士保罗谢勒研究所Ming Shi及其研究小组与中国科学院物理研究所的高鸿钧以及中国科学院理论物理研究所的吴贤新等人合作并取得一项新进展。经过不懈努力，他们发现钛基笼目超导体的非平凡带拓扑和轨道选择电子向列性。相关研究成果已于2023年9月21日在国际知名学术期刊《自然—物理学》上发表。
本文揭示了多轨道RbTi3Bi5的能带拓扑结构和轨道特性。研究人员使用了偏振依赖的角度分辨光发射光谱和密度泛函理论来识别该化合物中平带、II型狄拉克节点线和非平凡拓扑的共存。这项研究证明了笼目带在费米表面引起的轨道特征的变化，这意味着钛基笼目金属具有很强的内在轨道间耦合。
此外，与掺杂相关的测量揭示了笼目带的轨道选择性特征，这可以用d-p杂化来解释。因此，轨道间耦合和d-p杂化可能是ATi3Bi5中电子向列性的起源。
据悉，电子向列性自发破坏旋转对称性是高温超导体和笼目超导体AV3Sb5 (A可以是K, Rb或Cs)相关量子系统中的普遍现象。然而，这些系统中向列性的潜在机制很难识别，因为它与其他有序相纠缠。最近，合成了一类钛基笼目超导体ATi3Bi5，其中电子向列性发生在没有电荷有序的情况下。它提供了一个平台来研究纯形式的向列性以及它与轨道自由度的相互作用。
附：英文原文
Title: Non-trivial band topology and orbital-selective electronic nematicity in a titanium-based kagome superconductor
Author: Hu, Yong, Le, Congcong, Zhang, Yuhang, Zhao, Zhen, Liu, Jiali, Ma, Junzhang, Plumb, Nicholas C., Radovic, Milan, Chen, Hui, Schnyder, Andreas P., Wu, Xianxin, Dong, Xiaoli, Hu, Jiangping, Yang, Haitao, Gao, Hong-Jun, Shi, Ming
Issue&Volume: 2023-09-21
Abstract: Electronic nematicity that spontaneously breaks rotational symmetry is a generic phenomenon in correlated quantum systems including high-temperature superconductors and the AV3Sb5 (A can be K, Rb or Cs) family of kagome superconductors. However, the underlying mechanism of nematicity in these systems is hard to identify because of its entanglement with other ordered phases. Recently, a family of titanium-based kagome superconductors ATi3Bi5 have been synthesized, where electronic nematicity occurs in the absence of charge order. It provides a platform to study nematicity in its pure form, as well as its interplay with orbital degrees of freedom. Here we reveal the band topology and orbital characters of the multiorbital RbTi3Bi5. We use polarization-dependent angle-resolved photoemission spectroscopy with density functional theory to identify the coexistence of flat bands, type-II Dirac nodal lines and non-trivial topology in this compound. Our study demonstrates the change in orbital character along the Fermi surface contributed by the kagome bands, implying a strong intrinsic interorbital coupling in the Ti-based kagome metals. Furthermore, doping-dependent measurements uncover the orbital-selective features in the kagome bands, which can be explained by d–p hybridization. Hence, interorbital coupling together with d–p hybridization is probably the origin of electronic nematicity in ATi3Bi5.
DOI: 10.1038/s41567-023-02215-z
Source: https://www.nature.com/articles/s41567-023-02215-z