Crucial role of out-of-plane Sb-$p$ orbitals in Van Hove singularity formation and electronic correlation for superconducting Kagome metal CsV$_3$Sb$_5$

TL;DR

This study reveals that out-of-plane Sb-$p$ orbitals are crucial for the formation of Van Hove singularities and influence electronic correlations in the superconducting Kagome metal CsV$_3$Sb$_5$, with implications for tuning its properties.

Contribution

It identifies the out-of-plane Sb-$p$ orbital as essential for accurately describing Van Hove singularities and electronic interactions in CsV$_3$Sb$_5$, providing new insights into its electronic structure.

Findings

Out-of-plane Sb-$p$ orbitals are key to Van Hove singularity formation.

Sb-$p$ orbitals significantly affect electronic correlation parameters.

Strain and pressure can tune Van Hove singularities via Sb-$p$ orbital effects.

Abstract

First-principles density functional theory calculations are performed to understand the electronic structure and interaction parameters for recently discovered superconducting Kagome metal CsV$_3$Sb$_5$. A systematic analysis of the tight-binding parameters based on maximally localized Wannier function method demonstrates that the out-of-plane Sb$^{\rm out}$-$p$ orbital is a key element in complete description of the three Van Hove singularity structures known in this material at $M$ point near the Fermi level. Further, the correlation strengths are also largely determined by Sb$^{\rm out}$-$p$ states. Based on constrained random phase approximation, we find that on-site and inter-site interaction parameter are both significantly affected by the screening effect of Sb$^{\rm out}$-$p$ orbitals. As the role of this previously unnoticed orbital state can be tuned or controlled by out-of-plane lattice parameters, we examine the electronic structure and particularly the evolution of Van Hove singularity points as a function of strain and pressure, which can serve as useful knobs to control the material properties.