Crystal structure, properties and pressure-induced insulator-metal transition in layered kagome chalcogenides

• Published in: arXiv.org 2024-06
• Main Authors: Du, Hong, Zheng, Yu, Cuiying Pei, Chi-Ming Yim, Qi, Yanpeng, Zhong, Ruidan
• Format: Article
• Language: English
• Subjects: Alkali metals; Cesium; Crystal growth; Crystal structure; Electron states; Kagome lattice; Layered materials; Magnetic properties; Palladium; Phase transitions; Rubidium; Single crystals; Transition metals; Transport properties
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2403.05001

Layered materials with kagome lattice have attracted a lot of attention due to the presence of nontrivial topological bands and correlated electronic states with tunability. In this work, we investigate a unique van der Waals (vdW) material system, \(A_{2}M_{3}X_{4}\) (\(A\) = K, Rb, Cs; \(M\) = Ni, Pd; \(X\) = S, Se), where transition metal kagome lattices, chalcogen honeycomb lattices and alkali metal triangular lattices coexist simultaneously. A notable feature of this material is that each Ni/Pd atom is positioned in the center of four chalcogen atoms, forming a local square-planar environment. This crystal field environment results in a low spin state \(S\) = 0 of Ni\(^{2+}\)/Pd\(^{2+}\). A systematic study of the crystal growth, crystal structure, magnetic and transport properties of two representative compounds, Rb\(_{2}\)Ni\(_{3}\)S\(_{4}\) and Cs\(_{2}\)Ni\(_{3}\)Se\(_{4}\), has been carried out on powder and single crystal samples. Both compounds exhibit nonmagnetic \(p\)-type semiconducting behavior, closely related to the particular chemical environment of Ni\(^{2+}\) ions and the alkali metal intercalated vdW structure. Additionally, Cs\(_{2}\)Ni\(_{3}\)Se\(_{4}\) undergoes an insulator-metal transition (IMT) in transport measurements under pressure up to 87.10 GPa without any structural phase transition, while Rb\(_{2}\)Ni\(_{3}\)S\(_{4}\) persists in its semiconducting behavior.