Zhao He, Li Hong, Ortiz Brenden R, Teicher Samuel M L, Park Takamori, Ye Mengxing, Wang Ziqiang, Balents Leon, Wilson Stephen D, Zeljkovic Ilija
Department of Physics, Boston College, Chestnut Hill, MA, USA.
Materials Department and California Nanosystems Institute, University of California Santa Barbara, Santa Barbara, CA, USA.
Nature. 2021 Nov;599(7884):216-221. doi: 10.1038/s41586-021-03946-w. Epub 2021 Sep 29.
The kagome lattice of transition metal atoms provides an exciting platform to study electronic correlations in the presence of geometric frustration and nontrivial band topology, which continues to bear surprises. Here, using spectroscopic imaging scanning tunnelling microscopy, we discover a temperature-dependent cascade of different symmetry-broken electronic states in a new kagome superconductor, CsVSb. We reveal, at a temperature far above the superconducting transition temperature T ~ 2.5 K, a tri-directional charge order with a 2a period that breaks the translation symmetry of the lattice. As the system is cooled down towards T, we observe a prominent V-shaped spectral gap opening at the Fermi level and an additional breaking of the six-fold rotational symmetry, which persists through the superconducting transition. This rotational symmetry breaking is observed as the emergence of an additional 4a unidirectional charge order and strongly anisotropic scattering in differential conductance maps. The latter can be directly attributed to the orbital-selective renormalization of the vanadium kagome bands. Our experiments reveal a complex landscape of electronic states that can coexist on a kagome lattice, and highlight intriguing parallels to high-T superconductors and twisted bilayer graphene.
过渡金属原子的 Kagome 晶格为研究几何阻挫和非平凡能带拓扑结构下的电子关联提供了一个令人兴奋的平台，该领域仍不断带来惊喜。在此，我们使用光谱成像扫描隧道显微镜，在一种新型 Kagome 超导体 CsVSb 中发现了一系列依赖于温度的不同对称性破缺电子态。我们揭示，在远高于超导转变温度 T ≈ 2.5 K 的温度下，存在一种具有 2a 周期的三向电荷序，它打破了晶格的平移对称性。当系统冷却至 T 时，我们观察到在费米能级处出现一个显著的 V 形能隙，以及六重旋转对称性的额外破缺，这种破缺在超导转变过程中持续存在。这种旋转对称性破缺表现为出现额外的 4a 单向电荷序以及在微分电导图中出现强烈的各向异性散射。后者可直接归因于钒 Kagome 能带的轨道选择性重整化。我们的实验揭示了 Kagome 晶格上可能共存的复杂电子态图景，并突出了与高温超导体和扭曲双层石墨烯的有趣相似之处。
