master thesis
Gregor Jecl (Author), Dragan Mihailović (Mentor), Venera Nasretdinova (Co-mentor), Yaroslav Gerasimenko (Co-mentor)

Abstract

By 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.

Keywords

optical spectroscopy;phase transitions;relaxation processes;alloys;superconducting materials;metastable phases;collective effects;

Data

Language: English
Year of publishing:
Typology: 2.09 - Master's Thesis
Organization: UL FMF - Faculty of Mathematics and Physics
Publisher: [G. Jecl]
UDC: 538.9
COBISS: 56630787 Link will open in a new window
Views: 443
Downloads: 109
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Other data

Secondary language: Slovenian
Secondary title: Časovno-ločjive raziskave ultrahitre strukturne dinamike valenčne modulacije iridija v IrTe$_2$
Secondary abstract: Z ultrahitro časovno-ločljivo optično spektroskopijo smo raziskovali relaksacijsko dinamiko v IrTe$_2$, plastovitem, kvazi-2D materialu, ki je znan po nenavadnih faznih prehodih, po fazah z ureditvijo naboja pri temperaturah, nižjih od $\sim 280$ K, in po pojavu superprevodnosti v dopiranem materialu ali v nedopiranih tankih vzorcih. Opazovali smo relaksacijsko dinamiko materiala po vzbuditvi s šibkimi ultrakratkimi laserskimi sunki v temperaturnem območju med $10$ K in $300$ K, ter pri nizkih temperaturah ob močni fotovzbuditvi. V limiti šibke vzbuditve smo identificirali vse strukturne faze materiala ter opazili njihovo histerezo. V eksperimentih pod močno fotovzbuditvijo smo opazili spremenjen režim relaksacije in značilnosti neobstojne, fotovzbujene mešanice različnih strukturnih faz. V eksperimentih s tri-pulzno metodo pri nizkih temperaturah smo prav tako opazili značilnosti začasnega fotoinduciranega faznega prehoda v višje temperaturno stanje, ki se sprosti nazaj v začetno stanje po $\sim 100-150$ ps.
Secondary keywords: optična spektroskopija;fazni prehodi;relaksacijski procesi;zlitine;superprevodnost;metastabilne faze;kolektivni efekti;
Type (COBISS): Master's thesis/paper
Study programme: 0
Thesis comment: Univ. v Ljubljani, Fak. za matematiko in fiziko, Oddelek za fiziko
Pages: 90 str.
ID: 12671648