Pressure induced insulator-metal transition in LaMnO3

J. D. FUHR; B. ALASCIO; M. AVIGNON

REVISTA MEXICANA DE FíSICA

Año: 2007 vol. 53 p. 29 - 33

0035-001X

The recent observation of an insulator to metal transition (IMT) [1] in pure LaMnO3 at 32 GPa and at room temperature, well above the Neel temperature (145 K) and below the Jahn-Teller transition temperature (780 K), opens the way to a study of the role of the orbital degrees of freedom on the electronic structure in a stoichiometric material. In this paper we focus our attention on the orbital aspects of the insulator to metal transition. We use a Hamiltonian model for the eg orbitals of Mn that includes the on site Coulomb repulsion U , the hopping t, and its pressure dependence. In order to include in an appropriate way the strong correlations induced by the dominant electron-electron interactions, we introduce auxiliary fields (Slave Bosons,SB) to the description of the low energy states. We use the O-Mn distance (d) dependence of it according to [2] and the pressure-d relation from the experimental data to describe the evolution of the electronic structure with pressure. Our results confirm and make transparent the conclusion reached in previous ab-initio calculations: the inclusion of the Coulomb energy is necessary and constitutes an important factor enhancing the orbital polarization in these compounds.