Weakened electron phonon coupling and delocalization effect in Pr and Ru co-doped Mott insulator Sr2IrO4-δ

The antiferromagnetic Mott insulator Sr2IrO4 exhibits an anomalous metal-to-insulator transition (MIT) rooted in the strong coupling among spin, charge, and lattice degrees of freedom. Doping can effectively modulate the Mott gap and influence the MIT. Here, we systematically investigate the electrical transport properties, magnetic orders and phonon vibration modes of Ru and Pr codoped Sr2IrO4-δ. In Sr1.97Pr0.07Ir1-xRuxO4-δ (0 ≤ x ≤ 0.65), with increasing Ru doping, the conductivity changes from insulating to metallic states, accompanied by the suppression of antiferromagnetic order and phonon softening. While in Sr2-yPryRu0.44Ir0.56O4-δ (0 ≤ y ≤ 0.11), the conductivity, magnetism, and phonon modes are non-monotonic dependence on Pr doping. We attribute these effects to the change of Ir(Ru)-O-Ir(Ru) bond angle and an out-of-phase displacement of Sr(Pr) along c-axis, which delocalize the Ir(Ru) electrons and weaken the electron-phonon coupling effect. Additionally, it implies a competing interaction between the rotation of Ir(Ru)O6 octahedra and the displacement of Sr(Pr). This work offers insight into the interactions between phonons, electrons, and spins in the antiferromagnetic Mott insulator Sr2IrO4-δ. The antiferromagnetic Mott insulator Sr2IrO4 exhibits an anomalous metal-to-insulator transition rooted in spin, charge, and lattice degrees of freedom. Doping provides an effective means to tailor the Mott gap, thereby modulating the transition behavior. In this work, we carry out a systematic investigation of the electrical transport properties, magnetic ordering, and phonon vibration modes in Ru- and Pr- co-doped Sr2IrO4-δ. This work offers insight into the interactions between phonons, electrons, and spins in the antiferromagnetic Mott insulator Sr2IrO4.