Ding, P.; Lin, J.-F.; Sun, P.; Lou, R.; Fedorov, A.; He, Z.-X.; Ma, H.; Zhou, Z.; Büchner, B.; Chen, X.; Liu, K.; Xia, T.-L.; Wang, S.: Emergence of monolayer electron behavior in bulk van der Waals superlattice. Physical Review B 109 (2024), p. 155115/1-7
10.1103/PhysRevB.109.155115
Abstract:
Monolayer transition metal dichalcogenides (TMDs) have a simple crystal structure, but they exhibit intricate physical phenomena that differ from their bulk counterparts. Recently, there has been significant interest in the electronic behavior of monolayer TMDs hosted in a natural van der Waals superlattice material, Ba6Nb11S28, consisting of alternating NbS2 monolayers and block layers. Here, we report the electronic structure study of Ba6Nb11S28 and Ba6Ta11S28. Using angle-resolved photoemission spectroscopy and density functional theory calculation, we show that the electronic structures of the superlattices are similar to those of monolayer TMDs. The two-dimensional characteristics indicate that the interlayer coupling of adjacent TMD layers is suppressed by the intercalation of the Ba3NbS5 or Ba3TaS5 block layer. A clear band splitting due to spin-orbital coupling is observed in Ba6Ta11S28, while no obvious splitting is found in Ba6Nb11S28. These observations are in qualitative agreement with the observation on monolayer films of NbS2 and TaS2. Based on our findings, these natural superlattices can serve as an effective model system for studying monolayer materials and their potential applications.