Crucial role of out-of-plane Sb <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>p</mml:mi></mml:math> orbitals in Van Hove singularity formation and electronic correlations in the superconducting kagome metal <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>CsV</mml:mi><mml:mn>3</mml:mn></mml:msub><mml:msub><mml:mi>Sb</mml:mi><mml:mn>5</mml:mn></mml:msub></mml:mrow></mml:math>

Abstract

First-principles density functional theory calculations are performed to understand the electronic structure and interaction parameters for recently discovered superconducting kagome metal ${\mathrm{CsV}}_{3}{\mathrm{Sb}}_{5}$. A systematic analysis of the tight-binding parameters based on the maximally localized Wannier function method demonstrates that the out-of-plane ${\mathrm{Sb}}^{\mathrm{out}}\text{\ensuremath{-}}p$ orbital is a key element in complete description of the three Van Hove singularity structures known in this material at the $M$ point near the Fermi level. Further, the correlation strengths are also largely determined by ${\mathrm{Sb}}^{\mathrm{out}}\text{\ensuremath{-}}p$ states. Based on the constrained random phase approximation, we find that the on-site and intersite interaction parameter are both significantly affected by the screening effect of ${\mathrm{Sb}}^{\mathrm{out}}\text{\ensuremath{-}}p$ 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.

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