Calculation of model Hamiltonian parameters for LaMnO_3 using maximally localized Wannier functions

TL;DR

This paper constructs maximally localized Wannier functions for LaMnO_3 to derive accurate model Hamiltonian parameters, revealing limitations of simplified models due to neglecting Mn(d)-O(p) hybridization effects.

Contribution

It systematically derives model parameters for LaMnO_3 using MLWFs and highlights the importance of including hybridization effects in manganite models.

Findings

Calculated Jahn-Teller and Hund's rule couplings

Determined hopping amplitudes and their reduction due to distortions

Identified limitations of common simplified models

Abstract

Maximally localized Wannier functions (MLWFs) based on Kohn-Sham band-structures provide a systematic way to construct realistic, materials specific tight-binding models for further theoretical analysis. Here, we construct MLWFs for the Mn e_g bands in LaMnO_3, and we monitor changes in the MLWF matrix elements induced by different magnetic configurations and structural distortions. From this we obtain values for the local Jahn-Teller and Hund's rule coupling strength, the hopping amplitudes between all nearest and further neighbors, and the corresponding reduction due to the GdFeO_3-type distortion. By comparing our results with commonly used model Hamiltonians for manganites, where electrons can hop between two "e_g-like" orbitals located on each Mn site, we find that the most crucial limitation of such models stems from neglecting changes in the underlying Mn(d)-O(p) hybridization.