A new concept is proposed for the paramagnetic metal insulator transition in the layer perovskite Ca_{2-x}Sr_xRuO_4. Whereas the pure Sr compound is metallic up to very large Coulomb energies due to strong orbital fluctuations, structural changes induced by doping with Ca give rise to a interorbital charge transfer which makes the material extremely sensitive to local correlations. Using dynamical mean field theory based on finite temperature multi-band exact diagonalization it is shown that the combination of crystal field splitting and onsite Coulomb interactions leads to complete filling of the d_xy band and to a Mott transition in the half-filled d_xz,yz bands.
@article{arxiv.cond-mat/0612539,
title = {Subband filling and Mott transition in Ca_{2-x}Sr_xRuO_4},
author = {A. Liebsch and H. Ishida},
journal= {arXiv preprint arXiv:cond-mat/0612539},
year = {2009}
}