Time-resolved optical studies of ultrafast structural dynamics of the valency modulation of iridium in IrTe$_2$Jecl, Gregor (Avtor) Mihailović, Dragan (Mentor) Gerasimenko, Yaroslav (Komentor) Nasretdinova, Venera (Komentor) Ultrafast time-resolved optical spectroscopysolid-solid transitionsrelaxation processes in metals and alloyssuperconducting materials (noncuprates)metastable phasescollective effectsBy employing ultrafast time-domain reflectivity spectroscopy we have studied the relaxation dynamics in IrTe$_2$, a layered, quasi-2D material known for its unusual structural phase transitions, the appearance of charge ordered phases under $\sim 280$ K and for the emergence of superconductivity in doped bulk samples and in thin flakes of the pristine compound. We have studied the pump-induced relaxation behaviour of the material in the temperature range between $10$ K and $300$ K in the linear regime of excitation, as well as at low temperatures in the strong excitation regime. From weak excitation experiments we have been able to identify all of the structural phases of the material and have observed the reported structural hysteresis. Experiments under strong photoexcitation reveal modified relaxation behaviour with signatures of a transient, non-thermal photoinduced mixture of multiple charge orders. In additional low-temperature three-pulse pump-probe experiments we observe further evidence of a transient photoinduced transition to a higher temperature state, which slowly relaxes back into the initial state after $\sim 100-150$ ps.20212021-03-21 08:15:03Magistrsko delo/naloga125516VisID: 117944COBISS_ID: 56630787sl