We present a correlated {\it ab initio} description of the paramagnetic phase of Tl2Mn2O7, employing a combined local density approximation (LDA) with multiorbital dynamical mean field theory (DMFT) treatment. We show that the insulating state observed in this colossal magnetoresistance (CMR) pyrochlore is determined by strong Mn intra- and inter-orbital local electron-electron interactions. Hybridization effects are reinforced by the correlation-induced spectral weight transfer. Our result coincides with optical conductivity measurements, whose low energy features are remarkably accounted for by our theory. Based on this agreement, we study the disorder-driven insulator-metal transition of doped compounds, showing the proximity of Tl2Mn2O7 to quantum phase transitions, in agreement with recent measurements.
@article{arxiv.cond-mat/0509153,
title = {Mott-Hubbard quantum criticality in paramagnetic CMR pyrochlores},
author = {L. Craco and C. I. Ventura and A. N. Yaresko and E. Müller-Hartmann},
journal= {arXiv preprint arXiv:cond-mat/0509153},
year = {2009}
}