Drastic electronic structure reconstruction of Ca$_{1-x}$Pr$_x$Fe$_2$As$_2$ in the collapsed tetragonal phase

TL;DR

This study reveals significant electronic structure changes in Ca$_{1-x}$Pr$_x$Fe$_2$As$_2$ during the collapsed tetragonal phase, highlighting the persistence of hole Fermi surfaces and the emergence of dispersive electron bands, which suggest correlation weakening over Fermi surface nesting as the key factor.

Contribution

It provides detailed ARPES measurements showing the electronic structure of Ca$_{1-x}$Pr$_x$Fe$_2$As$_2$ in the CT phase, contrasting with other FeAs compounds, and proposes a new understanding of the phase's electronic properties.

Findings

Hole Fermi surface persists in CT phase.

Multiple dispersive electron-like bands observed.

Correlation weakening may suppress magnetic order and superconductivity.

Abstract

We report the electronic structure reconstruction of Ca$_{1-x}$Pr$_x$Fe$_2$As$_2$ ($x$ = 0.1 and 0.15) in the low temperature collapsed tetragonal (CT) phase observed by angle-resolved photoemission spectroscopy. Different from Ca(Fe$_{1-x}$Rh$_x$)$_2$As$_2$ and the annealed CaFe$_2$As$_2$ where all hole Fermi surfaces are absent in their CT phases, the cylindrical hole Fermi surface can still be observed in the CT phase of Ca$_{1-x}$Pr$_x$Fe$_2$As$_2$. Furthermore, we found at least three well separated electron-like bands around the zone corner in the CT phase of Ca$_{1-x}$Pr$_x$Fe$_2$As$_2$, which are more dispersive than the electron-like bands in the high temperature tetragonal phase. Based on these observations, we propose that the weakening of correlations (as indicated by the reduced effective mass), rather than the lack of Fermi surface nesting, might be responsible for the absence of magnetic ordering and superconductivity in the CT phase.