Pressure effects on the electronic structure of the kagome metal CsV3Sb5

Abstract

This study explores the electronic and structural properties of the kagome metal CsV3Sb5 under uniaxial pressures up to 20 GPa, utilizing first-principles calculations based on experimental crystallographic data provided by Tsirlin et al., SciPost Phys. 12, 049 (2022). At ambient pressure, the electronic band structure exhibits multiple Dirac points, van Hove singularities (VHSs), and flat bands near the Fermi level, which progressively shift closer to the Fermi level with increasing pressure. Remarkably, two additional Dirac-like crossings emerge above 4.9 GPa, moving ∼25 meV below the Fermi level at 20 GPa. Concurrently, the VHS crosses the Fermi level as pressure increases to 9.8 GPa, highlighting a dynamic evolution of the electronic structure under high pressure conditions. The Fermi surface evolution under pressure reveals quasi-2D pockets, including a deformed cylindrical pocket centered at the Γ-point and a hexagonal pocket at the Brillouin zone boundary. Notably, the cylindrical pocket splits into two semi-spherical pockets above 4.9 GPa. Phonon calculations indicate lattice dynamical instability at ambient pressure, as evidenced by negative phonon frequencies, but stabilization occurs above 4.9 GPa, where all phonon modes become positive. These findings provide crucial insights into the pressure-induced modifications in the electronic and structural properties of CsV3Sb5, advancing the understanding of kagome-based quantum materials and their emergent phenomena.