Orbitally driven insulator-metal transition in CuIr2S4: Temperature-dependent transient reflectivity study

Ultrafast transient reflectivity across the unusual three-dimensional Peierls-like insulator-metal (IM) transition in CuIr2S4 was measured as a function of temperature. The low-temperature insulating-phase transient response is dominated by broken-symmetry-induced coherent lattice oscillations that abruptly vanish at the IM transition. The coherent mode spectra are consistent with Raman spectra reported in literature. The origin of the broken-symmetry-induced modes and the photoexcited carrier recombination pathway through in-gap defect states are also briefly discussed.