Abstract

We investigated the electronic properties of a single crystal of metallic pyrochlore iridate Bi2Ir2O7 by means of infrared spectroscopy. Our optical conductivity data show the splitting of t(2g) bands into J(eff) ones due to strong spin-orbit coupling. We observed a sizable midinfrared absorption near 0.2 eV which can be attributed to the optical transition within the J(eff, 1/2) bands. More interestingly, we found an abrupt suppression of optical conductivity in the very far-infrared region. Our results suggest that the electronic structure of Bi2Ir2O7 is governed by the strong spin-orbit coupling and correlation effects, which are a prerequisite for theoretically proposed nontrivial topological phases in pyrochlore iridates.