Electronic structure of Pr$_{1-x}$Ca$_x$MnO$_3$

TL;DR

This study combines theoretical and experimental methods to analyze the electronic structure of Pr$_{1-x}$Ca$_x$MnO$_3$ across various compositions and magnetic orders, revealing the roles of electron-phonon coupling and orbital occupation.

Contribution

It provides a comprehensive model Hamiltonian and a local-orbital interpretation that unify experimental spectra with first-principles calculations for this material.

Findings

Optical spectra variations linked to magnetic order and orbital occupation.

Partial Coulomb parameter cancellation suggests electron-phonon coupling dominance.

A validated model Hamiltonian applicable across doping levels.

Abstract

The electronic structure of Pr$_{1-x}$Ca$_x$MnO$_3$ has been investigated using a combination of first-principles calculations, X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), electron-energy loss spectroscopy (EELS), and optical absorption. The full range of compositions, $x=0,1/2,1$, and a variety of magnetic orders have been covered. Jahn-Teller as well as Zener polaron orders are considered. The free parameters of the local hybrid density functionals used in this study has been determined by comparison with measured XPS spectra. A model Hamiltonian, valid for the entire doping range, has been extracted. A simple local-orbital picture of the electronic structure for the interpretation of experimental spectra is provided. The comparison of theoretical calculations and different experimental sprectra provide a detailed and consistent picture of the electronic structure. The large variations of measured optical absorption spectra are traced back to the coexistence of magnetic orders respectively to the occupation of local orbitals. A consistent treatment of the Coulomb interaction indicate a partial cancellation of Coulomb parameters and support the dominance of the electron-phonon coupling.