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| STRIPEX – Vplyv dynamických nábojových pásov na kvantové magnety a supravodiče v extrémnych podmienkach | |
| Influence of dynamic charge stripes on quantum magnets and superconductors in extreme conditions | |
| Program: | SRDA |
| Project leader: | doc. RNDr. Gabáni Slavomír, PhD. |
| Annotation: | The project is aimed at solving the urgent fundamental problem of the genesis of the so-called of dynamic charge stripes (DCS) – inhomogeneous distribution of conduction electron oscillations – and their influence on the properties of strongly correlated electron systems (SCES). The charge stripes play an important role in the high-temperature superconductivity (HTSC) of cuprates and also underlie the mechanisms responsible for the colossal magnetoresistance in manganites, cobaltites, iron-based HTSCs, etc. Observing directly the effect of DCS on the scattering of charge carriers in the mentioned SCES is very sophisticated due to their complex composition, low symmetry of the crystal structure and high sensitivity to external conditions. Instead, it is suitable to use model SCES. Such model materials are rare earth dodecaborides (RB12) with Jahn-Teller structural instability and electronic phase separation on the nanoscale range, in which the appearance of dynamic charge stripes was reliably determined for the first time both for superconductors (ZrB12, LuB12) and for quantum magnets (R = Ho, Er, Tm). The comprehensive study of DCS will be extended by additional model systems based on hexaborides (RB6) and frustrated quantum magnets based on rare earth tetraborides (RB4), and will includes the influence of external extreme conditions such as very low temperatures, high magnetic fields and pressures. |
| Duration: | 1.7.2024 – 30.6.2028 |
| Teoretické štúdium kooperatívnych javov v silne korelovaných elektrónových a spinových systémoch | |
| Theoretical study of cooperative phenomena in strongly correlated electron and spin systems | |
| Program: | VEGA |
| Project leader: | RNDr. Farkašovský Pavol, DrSc. |
| Annotation: | The proposed project is devoted to the theoretical study of cooperative phenomena in strongly correlated electron and spin systems. The special attention will be paid to specifying the key mechanisms which lead to formation and stabilization of inhomogeneous charge and spin ordering, superconductivity, itinerant ferromagnetism, ferroelectric and magnetocaloric phenomenon due to the big application potential of these phenomena and their possible coexistence. The study will be performed on comprehensive model, which will take into account all relevant interactions in rare-earth and transition metal compounds, where besides the spin-independent Coulomb interaction in d and f band also the spin dependent (double exchange) interaction between both bands will be included. For a solution of this model we plan to elaborate new numerical methods, which will be subsequently used in combination with standard methods of quantum statistical physics (DMRG and QMC) to study the above mentioned phenomena. |
| Duration: | 1.1.2022 – 31.12.2025 |
| Teoretické štúdium frustrovaných magnetických systémov | |
| Theoretical study of frustrated magnetic systems | |
| Program: | SRDA |
| Project leader: | RNDr. Jurčišin Marián, PhD. |
| Duration: | 1.7.2021 – 30.6.2025 |
| FRUSTKOM – Frustrované kovové magnetické systémy | |
| Frustrated metallic magnetic systems | |
| Program: | SRDA |
| Project leader: | doc. RNDr. Gabáni Slavomír, PhD. |
| Annotation: | The up to now experimental and theoretical studies of frustrated magnetic systems (FMS) has been concentrated mainly on dielectric systems. Such systems can be found in 2D and 3D lattices based on equilateral triangles, and in dielectrics the interaction between their spins can be relatively well defined and described. In metallic FMS (M-FMS), which have been much less studied, an important role plays the long-range indirect exchange interaction between the spins mediated by conduction electrons (the RKKY interaction). To the small number of up to now studied M-FMS belong also some rare earth metallic borides having a fcc (e.g.HoB12, ErB12) or Shastry-Sutherland (e.g.TmB4, HoB4, ErB4) structure. This project aims are to investigate experimentally the impact of high pressure (hydrostatic and uniaxial), the influence of alloying and the anisotropy on the magnetic, transport and thermal properties of M -FMS, which has not been studied yet. A pioneering work will be above all the direct observation of magnetic structures of individual phase diagram regions of these M-FMS by spin-polarized scanning tunnelling microscopy. Investigated will be also the dynamics of magnetic structures (the influence of the rate of change of the magnetic field on these structures) and the study of magnetic excitations (by neutron diffraction methods) in selected tetraborides and dodecaborides.The challenging experimental studies, for which both high quality samples and suitable methods are already available, will be supported by the theoretical interpretation of received results, and by the theoretical elaboration. |
| Project webpage: | http://extremeconditions.saske.sk/projects/ |
| Duration: | 1.8.2018 – 31.12.2022 |
| Systematické štúdium vplyvu lokálnych a nelokálnych interakcií na koexistenciu kvantových fáz s rôznymi parametrami usporiadania | |
| Systematic study of influence of local and nonlcal interactions on coexistence of quantum phases with different order parameters | |
| Program: | VEGA |
| Project leader: | RNDr. Farkašovský Pavol, DrSc. |
| Annotation: | The proposed project is focused on the complex study of influence of local and non-local interactions, of the Coulomb and spin nature, on the ground state properties of the generalized two-band Hubbard model. The results obtained will be used for a description of anomalous cooperative phenomena in real materials with strongly correlated electrons. The study will include a wide class of cooperative phenomena such as valence and metal-insulator transitions, charge and spin ordering, itinerant ferromagnetism, electronic ferroelectricity, supercoductivity, excitonic matter and will concern a wide class of materials such as nickelates, cobaltates, rare-earth hexaborides and chalcogenides,multiferroics, etc. The emphasis will be put on the study of influence of combined effects of two or more interactions with a goal to describe coexistence of two or more quantum phases with different order parameters (ferromagnetic-ferroelectric state, charge/spin ordering-superconductivity, etc.). |
| Duration: | 1.1.2018 – 31.12.2021 |