Self-doping induced orbital-selective Mott transition in Hg₂Ru₂O₇

Pyrochlore oxides are fascinating systems where strong multiorbital correlations in concert with geometrical frustration give rise to unanticipated physical properties. The detailed mechanism of the insulator-metal transitions (IMTs) underpinning these phenomena is, however, ill understood in general. Motivated thereby, we study the IMT in the pyrochlore Hg₂Ru₂O₇ using local-density approximation plus dynamical mean-field theory. In contrast to the well-known examples of Mott transitions in transition metal oxide, we show that in the negative charge-transfer situation characteristic of Hg₂Ru₂O₇, self-doping plays a crucial role in the emergence of an orbital-selective IMT. We argue that this mechanism has broader relevance to other correlated pyrochlore oxides.