Pressure Suppression of Electron Correlation in the Collapsed Tetragonal Phase of $CaFe_2As_2$ : A DFT-DMFT Investigation

TL;DR

This study uses DFT+DMFT calculations to analyze how pressure suppresses electron correlation in the collapsed tetragonal phase of CaFe2As2, revealing a transition from a bad metal to a good metal with reduced local moments.

Contribution

It provides a detailed theoretical investigation of electron correlation suppression in CaFe2As2's collapsed tetragonal phase using advanced computational methods.

Findings

Transition from bad metal to good metal under pressure

Suppression of local magnetic moments in the CT phase

Gain in optical kinetic energy due to reduced Hund's coupling

Abstract

Recent studies reveal a pressure induced transition from a paramagnetic tetragonal phase (T) to a collapsed tetragonal phase (CT) in $CaFe_2As_2$, which was found to be superconducting with non-hydrostatic pressure at low temperature. We have investigated the effects of electron correlation and local fluctuating moment in both tetragonal and collapsed tetragonal phases of the paramagnetic $CaFe_2As_2$ using self consistent DFT+DMFT with continuous time quantum Monte Carlo as the impurity solver. From the computed optical conductivity, we find a gain in the optical kinetic energy due to the loss in Hund's rule coupling energy in the CT. We find that the transition from T to CT turns $CaFe_2As_2$ from a bad metal into a good metal. Computed mass enhancement and local moments also show significant decrease in the CT, which confirms the suppression of the electron correlation in the CT phase of $CaFe_2As_2$.