Observation of flat and weakly dispersing bands in a van der Waals semiconductor Nb3Br8 with breathing kagome lattice

Abstract

Niobium halides, Nb3X8 (X = Cl,Br,I), which are predicted two-dimensional magnets, have recently gotten attention due to their breathing kagome geometry. Here, we have studied the electronic structure of Nb3Br8 by using angle-resolved photoemission spectroscopy (ARPES) and first-principles calculations. ARPES results depict the presence of multiple flat and weakly dispersing bands. These bands are well explained by the theoretical calculations, which show they have Nb d character indicating their origination from the Nb atoms forming the breathing kagome plane. This van der Waals material can be easily thinned down via mechanical exfoliation to the ultrathin limit and such ultrathin samples are stable as depicted from the time-dependent Raman spectroscopy measurements at room temperature. These results demonstrate that Nb3Br8 is an excellent material not only for studying breathing kagome induced flat band physics and its connection with magnetism, but also for heterostructure fabrication for application purposes.

24 pages, 12 figures, Supplemental Material included

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Cited by in corpus (11)

• Kagome metals
• Layer Control of Magneto-Optical Effects and Their Quantization in Spin-Valley Splitting Antiferromagnets
• Magnetoelectric behavior of breathing kagomé monolayers of ${\mathrm{Nb}}_3{(\mathrm{Cl},\mathrm{Br},\mathrm{I})}_8$ from first-principles calculations
• Molecular Orbital Electronic Instability in the van der Waals Kagome Semiconductor Nb${}_3$Cl${}_8$: Exploring Future Directions
• Direct evidence of intrinsic Mott state and its layer-parity oscillation in a breathing kagome crystal down to monolayer
• Manipulating Photogalvanic Effects in Two-Dimensional Multiferroic Breathing Kagome Materials
• Momentum-Resolved Fingerprint of Mottness in Layer-Dimerized Nb${}_3$Br${}_8$
• Designing Topological High-Order Van Hove Singularities: Twisted Bilayer Kagomé
• Evidence of Mott Insulator with Thermally Induced Melting Behavior in Kagome Compound Nb3Cl8
• From strong to weak correlations in breathing-mode kagome van der Waals materials: Nb${}_3$(F,Cl,Br,I)${}_8$ as a robust and versatile platform for many-body engineering
• Spin-polarized triplet excitonic insulators in Ta3X8 (X=I, Br) monolayers