Effect of Hubbard U on the construction of low energy Hamiltonians for LaMnO_3 via maximally localized Wannier functions

摘要

We use maximally localized Wannier functions to construct tight-binding (TB)parameterizations for the e_g bands of LaMnO_3 based on first principleselectronic structure calculations. We compare two different ways to representthe relevant bands around the Fermi level: i) a d-p model that includesatomic-like orbitals corresponding to both Mn(d) and O(p) states in the TBbasis, and ii) an effective e_g model that includes only two e_g-like Wannierfunctions per Mn site. We first establish the effect of the Jahn-Tellerdistortion within the d-p model, and then compare the TB representations forboth models obtained from GGA+U calculations with different values of theHubbard parameter U. We find that in the case of the d-p model the TBparameters are rather independent on the specific value of U, if compared withthe mean-field approximation of an appropriate multi-band Hubbard Hamiltonian.In contrast, the U dependence of the TB parameters for the effective e_g modelcannot easily be related to a corresponding mean-field Hubbard model, andtherefore these parameters depend critically on the specific value of U, andmore generally on the specific exchange-correlation functional, used in theelectronic structure calculation.