First-principles Investigations of Band Engineering in Topological Kagome Metals AV3Sb5 (A=K, Rb, Cs)

Sadhukhan, Supratik (2025) First-principles Investigations of Band Engineering in Topological Kagome Metals AV3Sb5 (A=K, Rb, Cs). Masters thesis, Indian Institute of Science Education and Research Kolkata.

Text (MS Dissertation of Supratik Sadhukhan (20MS002)) 20MS002_Thesis_file.pdf Restricted to Repository staff only Download (4MB)

Abstract

This thesis explores the prospect of engineering the electronic structure of the Kagome metal compounds AV3Sb5 (A = K, Rb, Cs) by going into the 2D limit using first-principles density functional theory (DFT) calculations. Motivated by the fact that in 2D limit the effects of electronic instabilities are enhanced and the ease of tunability and stability in 2D, electronic structure of few layer AV3Sb5 and heterostructures made from KV3Sb5 and CsV3Sb5 are studied. Electronic charge susceptibility calculations are also performed to check for the existence of a charge density wave state in the monolayer. Plane-wave pseudopotential DFT is used to calculate the electronic structure and the energetics to analyze the stability, and a tight binding model is used to calculate the electronic charge susceptibility. The results reveal that few layer AV3Sb5 and the heterostructures are stable with large negative cohesive energies and the heterostructures have adhesion energies similar to those of the pure few layer AV3Sb5. Presence of multiple Van Hove Singularities (VHSs) near Fermi level are observed in the electronic band structure of few layer AV3Sb5, with modulation in their energy by changing the layer thickness, alkali A and building heterostructures. The tuning of the VHSs indicates possibly enhanced correlated electron phenomena and electronic instabilities in few layer AV3Sb5 compared to the bulk. The electronic charge susceptibility calculations in monolayer indicates presence of charge density wave instabilities. This work provides a comprehensive overview of the electronic structure of AV3Sb5 pointing out the fact that in the 2D limit these compounds can be a good platform to study electronic instabilities and correlated phenomena and should inspire theorists and experimentalists to study these systems.

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