Spin-orbit coupling induced Mott transition in Ca${}_{2-x}$Sr${}_x$RuO${}_4$ (0<x<0.2)

Abstract

We propose a new mechanism for the paramagnetic metal-insulator transition in the layered perovskite Ca${}_{2-x}$Sr${}_x$RuO${}_4$ (0<x<0.2). The LDA+U approach including spin-orbit coupling is used to calculate the electronic structures. In Ca${}_2$RuO${}_4$, we show that the spin-orbit effect is strongly enhanced by the Coulomb repulsion, which leads to an insulating phase. When Ca is substituted by Sr, the effective spin-orbit splitting is reduced due to the increasing bandwidth of the degenerate $d_{xz}$ and $d_{yz}$ orbitals. For x=0.2, the compound is found to be metallic. We show that these results are in good agreement with the experimental phase diagram.

4 pages, 4 figures

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