71. Element-resolved study on the influence of a magnetic dopant on the exchange interaction in FePt on ultrashort timescalesJurij Urbančič, 2017, objavljeni povzetek znanstvenega prispevka na konferenci Opis: In this study, we investigate the optically induced ultrafast demagnetization dynamics of a FePt alloy doped with Mn atoms on the characteristic timescale of the exchange interaction of a few femtoseconds. We use high harmonic generation with photon energies in the XUV to gain elemental resolution in a femtosecond magneto-optical Kerr-effect experiment [1] in transversal geometry. Following up on earlier experiments, which showed the importance of the exchange interaction in the demagnetization process in alloys [2,3], we see clear differences in the dynamical responses of the three elements Fe, Pt, and Mn. Our results suggest, that the exchange coupling between the magnetic moments of the FePt alloy and the Mn dopant changes on ultrashort timescales.
Ključne besede: FePt, High Harmonic Generation, Laser, Magnetic Materials
Objavljeno: 22.05.2020; Ogledov: 20; Prenosov: 0 |
72. The role of non-equilibrium dynamics in photo-induced phase transitions of correlated materialsJurij Urbančič, 2015, objavljeni povzetek znanstvenega prispevka na konferenci Opis: We use femtosecond extreme-ultraviolet time- and angle-resolved photoelectron spectroscopy to study the ultrafast photo-induced suppression of the charge-density wave (CDW) in 1T-TiSe2. In the following non-equilibrium electron dynamics after femtosecond laser excitation, we see that hot-carrier multiplication is the primary driver for the ultrafast CDW suppression. As soon as the optically excited carriers have relaxed to a quasi-equilibrium hot Fermi-distribution electron gas, the CDW suppression stops. Theoretical calculations of the hot-carrier scattering processes and the screening properties further link the carrier multiplication to the observed CDW gap dynamics.
Ključne besede: Correlated Materials, High Harmonic Generation, ARPES
Objavljeno: 22.05.2020; Ogledov: 20; Prenosov: 0 |
73. Towards ultrafast X-ray condensed matter physics with MHz repetition rate HHG sourcesJurij Urbančič, 2015, objavljeni povzetek znanstvenega prispevka na konferenci Opis: In recent years, an increasing number of ultrafast material science experiments are based on the use of table-top high-harmonic generation (HHG) lightsources [1,2]. Despite the huge success of these first experiments, a major drawback has been the limited repetition rate of these lightsources, in particular with respect to all types of photoemission experiments. Here, we combine newly developed high-repetition rate HHG sources [3,4] with state-of-the-art element-specific magneto-optical Kerr experiments. The chances and prospects for future ultrafast materials science experiments with these lightsources will be discussed.
Ključne besede: High Harmonic Generation, X-Rays, Condensed Matter
Objavljeno: 22.05.2020; Ogledov: 16; Prenosov: 0 |
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76. Narrowband high harmonic pulses for trARPES using frequency-upconverted Ti:Sapphire lasersJurij Urbančič, objavljeni povzetek znanstvenega prispevka na konferenci Opis: trARPES using femtosecond XUV high harmonics has recently emerged as a powerful tool for investigating ultrafast quasiparticle dynamics in correlated-electron materials. However, the full potential of this approach has not yet been achieved because, to date, high harmonics generated by 800 nm wavelength Ti:Sapphire lasers required a trade-off between photon flux, energy and time resolution. Photoemission spectroscopy requires a quasi-monochromatic output, but dispersive optical elements that select a single harmonic can significantly reduce the photon flux and time resolution. Here we show that shorter wavelength driven high harmonic extreme-ultraviolet trARPES is superior to using 800 nm laser drivers since it eliminates the need for any spectral selection, thereby increasing photon flux and energy resolution while preserving excellent time resolution.
Ključne besede: HHG, ARPES, Laser
Objavljeno: 22.05.2020; Ogledov: 21; Prenosov: 0 |
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80. Statistical mechanics of DNA adsorption on a carbon nanotubeSh. A. Tonoyan, Davit Khechoyan, Yevgeni S. Mamasakhlisov, Artem V. Badasyan, 2020, objavljeni povzetek znanstvenega prispevka na konferenci Opis: The attraction between the polycyclic aromatic surface elements of carbon nanotubes (CNT) and the aro-
matic nucleotides of deoxyribonucleic acid (DNA) leads to reversible adsorption (physisorption) between
them. With the goal to provide the theoretical support to numerous technologies on the basis of DNA-CNT
hybrids, we propose a Hamiltonian formulation for the zipper model that accounts for relevant interactions
and allows for the processing of experimental data, which has awaited an available theory for a decade.
Ključne besede: DNA, CNT
Objavljeno: 22.05.2020; Ogledov: 33; Prenosov: 2
 Polno besedilo (2,96 MB) |
