Strain effects on electron correlations in epitaxial (111) Pr₂Ir₂O₇ thin films

Over the years, numerous unconventional phenomena have been discovered in the quantum critical regime of strongly correlated materials. Pyrochlore iridates A₂Ir₂O₇ (A = Y or rare-earth element) have been identified as ideal candidates for exploring such emergent physics, as their spin-orbit coupling and electron correlations can be tuned to induce quantum phase transitions. Most members of this family exhibit a metal-insulator transition accompanied by all-in/all-out (AIAO) antiferromagnetic (AF) ordering below a characteristic transition temperature, except for Pr₂Ir₂O₇ . However, recent studies have revealed that epitaxial strain can drive Pr₂Ir₂O₇ from a paramagnetic metal to an AIAO AF insulator, offering a new pathway to access its quantum critical regime. In this work, we carried out resonant inelastic X-ray scattering (RIXS) measurements on Pr₂Ir₂O₇ thin films at Ir L₃ edge to probe the magnetism and the electronic configuration of Ir associated with this strain-induced insulating state. We report the strain effects on crystal field splitting, spin-orbit excitons, and magnetic excitations. These measurements are supported by simulations showing that only specific orbitals are influenced by the anisotropic strain.