Collapsed Tetragonal Phase Transition of Ca(Fe1-xRhx)2As2Studied by Photoemission Spectroscopy

Abstract

We have investigated the changes in the band structure and core-level energy of Ca(Fe1-xRhx)2As2 across the tetragonal–collapsed tetragonal (T–cT) phase transition using photoemission spectroscopy. Angle-resolved photoemission spectroscopy clearly demonstrates that, at the Γ point in the Brillouin zone, a hole-like band that crosses the Fermi level in the T phase lowers its energy position and is completely filled in the cT phase. This indicates the disappearance of a hole-like Fermi surface around the zone center in the cT phase, which gives rise to the extinction of nesting. The relationship of the present results with the results of previous transport and magnetic studies is discussed. The temperature dependences of the As \(3d\) and Ca \(2p\) core levels show energy shifts toward higher and lower binding energies, respectively. These data constitute the first direct experimental results on electronic structure and chemical states across the T–cT transition.