Flat band separation and robust spin Berry curvature in bilayer kagome metals

• Published in: Nature physics 2023-08, Vol.19 (8), p.1135-1142
• Main Authors: Di Sante, Domenico, Bigi, Chiara, Eck, Philipp, Enzner, Stefan, Consiglio, Armando, Pokharel, Ganesh, Carrara, Pietro, Orgiani, Pasquale, Polewczyk, Vincent, Fujii, Jun, King, Phil D. C., Vobornik, Ivana, Rossi, Giorgio, Zeljkovic, Ilija, Wilson, Stephen D., Thomale, Ronny, Sangiovanni, Giorgio, Panaccione, Giancarlo, Mazzola, Federico
• Format: Article
• Language: English
• Subjects: 639/301/119/995; 639/766/119/2792/4128; Angular momentum; Atomic; Brillouin zones; Charge density waves; Classical and Continuum Physics; Complex Systems; Condensed Matter Physics; Curvature; Electron spin; electronic properties and materials; Electronic structure; Fruits; MATERIALS SCIENCE; Mathematical and Computational Physics; Metals; Molecular; Optical and Plasma Physics; Photoelectric emission; Physics; Physics and Astronomy; Rare earth elements; Robustness; Spin-orbit interactions; Theoretical; topological insulators; Topology
• ISSN: 1745-2473; 1745-2481
• DOI: 10.1038/s41567-023-02053-z

Kagome materials have emerged as a setting for emergent electronic phenomena that encompass different aspects of symmetry and topology. It is debated whether the XV 6 Sn 6 kagome family (where X is a rare-earth element), a recently discovered family of bilayer kagome metals, hosts a topologically non-trivial ground state resulting from the opening of spin–orbit coupling gaps. These states would carry a finite spin Berry curvature, and topological surface states. Here we investigate the spin and electronic structure of the XV 6 Sn 6 kagome family. We obtain evidence for a finite spin Berry curvature contribution at the centre of the Brillouin zone, where the nearly flat band detaches from the dispersing Dirac band because of spin–orbit coupling. In addition, the spin Berry curvature is further investigated in the charge density wave regime of ScV 6 Sn 6 and it is found to be robust against the onset of the temperature-driven ordered phase. Utilizing the sensitivity of angle-resolved photoemission spectroscopy to the spin and orbital angular momentum, our work unveils the spin Berry curvature of topological kagome metals and helps to define its spectroscopic fingerprint. The direct observation of spin Berry curvature, an important aspect of non-trivial band topology, has not been achieved in quantum materials. Now it is observed in a bilayer Kagome metal.