Ultrafast dynamics of strongly excited corelated statesNaseska, Mimoza (Avtor) Mertelj, Tomaž (Mentor) ultrafast spectroscopyphase transitionsorbital orderingmagnetoopticsmagnetic anisotropyRaman spectroscopyferromagnetismmagnon scatteringElectronic correlations alone or in combination with lattice degrees of freedom can often lead to existence of variety of exotic ground states like high temperature superconductivity, charge density wave ordering, colossal magnetoresistance etc. Different phases of a correlated system can often be transformed into each other by subtle external perturbations. An example of such perturbation is a laser pulse with duration of several tens of fs. Short pulses of this kind can initiate a phase transition from a ground state of the material to some final state which in some cases can be metastable. Using ultrafast time resolved spectroscopy we explored the dynamics of the first order phase transition between the insulating and metallic state of CuIr2S4. We showed that the structural dynamics in CuIr2S4 is dominated by the first-order transition nucleation kinetics which prevents the complete transition to the high temperature phase at large excitation densities on ultrafast (~10 ps) timescales. Additionally, we investigated the possibility of a photoinducing phase transition to a hidden or a metastable state. However, we have found no evidence that a femtosecond excitation could lead to a long-lived metastable state that is more conducting than the already known slowly-formed disordered weakly-conducting state. The existence of large spin-orbit coupling in materials allows us to study the photoinduced magnetic dynamics using short laser pulses. CeSb is a rare-earth pnictogen that has large spin-orbit coupling and quite complicated magnetic phase diagram with up to 25 different magnetic states. By exploiting the magneto-optical phenomena we studied the photoinduced excitations in CeSb on ultrafast timescales in the different phases that arise by changing the temperature or the external magnetic field. The qualitative and quantitative differences of the measured responses on ultrafast timescales in the different magnetic phases allowed us to construct a phase diagram of photoinduced magnetic excitations as a function of temperature and magnetic field.20222022-12-07 08:15:02Doktorsko delo/naloga142975VisID: 130062COBISS_ID: 132320771sl