Spin-orbit coupling induced Mott transition in Ca2-xSrxRuO4 (0 ≤ x ≤ 0.2)

We propose a mechanism for the paramagnetic metal-insulator transition in the layered perovskite Ca2-xSrxRuO4 (0 <= x <= 0.2). The LDA+U approach including spin-orbit coupling is used to calculate the electronic structures. In Ca2RuO4, 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.