Title: Emergent electronic structure of CaFe2As2,
Abstract: CaFe2As2 exhibits collapsed tetragonal (cT) structure and varied exotic
behavior under pressure at low temperatures that led to debate on linking the
structural changes to its exceptional electronic properties like
superconductivity, magnetism, etc. Here, we investigate the electronic
structure of CaFe2As2 forming in different structures employing density
functional theory. The results indicate better stability of the cT phase with
enhancement in hybridization induced effects and shift of the energy bands
towards lower energies. The Fermi surface centered around $\Gamma$ point
gradually vanishes with the increase in pressure. Consequently, the nesting
between the hole and electron Fermi surfaces associated to the spin density
wave state disappears indicating a pathway to achieve the proximity to quantum
fluctuations. The magnetic moment at the Fe sites diminishes in the cT phase
consistent with the magnetic susceptibility results. Notably, the hybridization
of Ca 4s states (Ca-layer may be treated as a charge reservoir layer akin to
those in cuprate superconductors) is significantly enhanced in the cT phase
revealing its relevance in its interesting electronic properties.