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Charge transport characterization of P3HT thin-film organic semiconductor
Matija Filipčič, 2021, research project (high school)

Abstract: The focus of this diploma seminar is to describe different types of charge transport theory and models used for finding mobility in semiconductors, more specifically focused on P3HT thin-film organic semiconductor. It also describes the time-of-flight method, which was used to measure the experimental data for P3HT with time dependent current I(t) curve. Another data set was obtained by performing Kinetic Monte Carlo (KMC) simulations using Miller-Abrahams hopping formalism. KMC was used to determine the material disorder, simulate I(t) curve and transit time for every charge carrier. Simulated data, different transit times and mobilities were then finally compared with experimental, in order to find agreements between the two.
Found in: osebi
Keywords: charge transport, P3HT, thin-film organic semiconductor
Published: 15.09.2021; Views: 159; Downloads: 0
.pdf Fulltext (590,08 KB)

Orbital-dependent electron dynamics in Fe-pnictide superconductors
A. Thamizhavel, Damjan Krizmancic, Giovanni De Ninno, Jurij Urbančič, Primož Rebernik Ribič, Barbara Ressel, Ganesh Adhikary, Kalobaran Maiti, Matija Stupar, 2018, original scientific article

Abstract: We report on orbital-dependent quasiparticle dynamics in EuFe 2 As 2, a parent compound of Fe-based superconductors, and a way to experimentally identify this behavior using time-and angle-resolved photoelectron spectroscopy across the spin density wave transition. We observe two different relaxation timescales for photoexcited d x z/d y z and d x y electrons. While the itinerant d x z/d y z electrons relax faster through the electron-electron scattering channel, d x y electrons form a quasiequilibrium state with the lattice due to their localized character, and the state decays slowly. Our findings suggest that electron correlation in Fe pnictides is an important property, which should carefully be taken into account when describing the electronic properties of both parent and carrier-doped compounds, and therefore establish a strong connection with cuprates
Found in: osebi
Keywords: photoelectron dynamics, Fe based superconductors
Published: 29.11.2018; Views: 1819; Downloads: 0
.pdf Fulltext (2,37 MB)

Coupling of autoionizing states by a chirped laser pulse
Barbara Ressel, Jurij Urbančič, Primož Rebernik Ribič, Špela Krušič, Žiga Barba, Mateja Hrast, Klemen Bučar, Andrej Mihelič, Matjaž Žitnik, Matija Stupar, David Gauthier, Giovanni De Ninno, 2020, published scientific conference contribution abstract

Abstract: We have observed the autoionization of the laser-coupled 2s2p 1Po and 2p2 1Se resonances in helium. The ions were collected while varying the frequency and delay of the extreme-ultraviolet (EUV) excitation pulse with respect to the linearly chirped visible (VIS) laser pulse. From the measured frequency-delay map the Autler- Townes splitting, the EUV-VIS cross-correlation and the linear chirp parameter were extracted.
Found in: osebi
Keywords: High Harmonic Generation
Published: 29.06.2020; Views: 1176; Downloads: 0
.pdf Fulltext (654,72 KB)

Orbital selective dynamics in Fe-pnictides triggered by polarized pump pulse excitations
Kalobaran Maiti, A. Thamizhavel, Giovanni De Ninno, Jurij Urbančič, Barbara Ressel, Matija Stupar, Primož Rebernik Ribič, Tanusree Saha, Ganesh Adhikary, 2021, original scientific article

Abstract: Quantum materials display exotic behaviours related to the interplay between temperature-driven phase transitions. Here, we study the electron dynamics in one such material, CaFe$_2$As$_2$, a parent Fe-based superconductor, employing time and angle-resolved photoemission spectroscopy. CaFe$_2$As$_2$ exhibits concomitant transition to spin density wave state and tetragonal to orthorhombic structure below 170 K. The Fermi surface of this material consists of three hole pockets ($\alpha$, $\beta$ and $\gamma$) around $\Gamma$-point and two electron pockets around $X$-point. The hole pockets have $d_{xy}$, $d_{yz}$ and $d_{zx}$ orbital symmetries. The $\beta$ band constituted by $d_{xz}$/$d_{yz}$ orbitals exhibit a gap across the magnetic phase transition. We discover that polarized pump pulses can induce excitations of electrons of a selected symmetry. More specifically, while $s$-polarized light (polarization vector perpendicular to the $xz$-plane) excites electrons corresponding to all the three hole bands, $p$-polarized light excites electrons essentially from ($\alpha$,$\beta$) bands which are responsible for magnetic order. Interestingly, within the magnetically ordered phase, the excitation due to the $p$-polarized pump pulses occur at a time scale of 50 fs, which is significantly faster than the excitation induced by $s$-polarized light ($\sim$ 200 fs). These results suggest that the relaxation of different ordered phases occurs at different time scales and this method can be used to achieve selective excitations to disentangle complexity in the study of quantum materials.
Found in: osebi
Keywords: Electronic structure, Pnictides and chalcogenides, Time-resolved spectroscopy
Published: 13.10.2021; Views: 136; Downloads: 0
.pdf Fulltext (9,56 MB)

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