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| Frustrované kvantové magnety – vplyv jednoosového tlaku | |
| Frustrated quantum magnets – impact of uniaxial pressure | |
| Program: | Mobility |
| Project leader: | doc. RNDr. Gabáni Slavomír, PhD. |
| Duration: | 1.1.2024 – 31.12.2025 |
| Výskum korelovaných a topologických fáz vo van der Waalsovských materiáloch | |
| Exploring correlated and topological phases in layered van der Waals quantum materials | |
| Program: | Mobility |
| Project leader: | Mgr. Szabó Pavol, CSc. |
| Annotation: | The project aims to explore novel quantum physics in heterostructures made of 2D materials focusing on emergent quantum phenomena induced by the spin-orbit coupling and its interplay with magnetism, topology, and superconductivity. We propose a study of van der Waals (vdW) heterostructures made of few-layer thin superconductors and ferromagnet and topological materials in order to study proximity effects on topologically induced superconductivity. The objective of the research is to build technological knowhow of sample preparation made of 2D materials, performing scanning tunneling microscopy and transport experiments which will be complemented by the state-of-the-art density functional theory calculations and tight-binding modeling of electronic structure to study quasiparticle interferences and transport properties. |
| Duration: | 1.1.2023 – 31.12.2024 |
| Supravodivosť v tenkých filmoch nitridov – materiály pre budúce kvatové zariadenia | |
| Superconductivity in nitride thin films – materials for future quantum devices | |
| Program: | Other |
| Project leader: | RNDr. Pristáš Gabriel, PhD. |
| Annotation: | The main aim of our common project is study superconductivity in nitride thin films. It was shown, that narrow NbN superconducting strips could be used forconstruction of ultrafast single photon detectors, which are expected to play important role in the secure quantum communications. Very recently, team from Montanuniversität Leoben succeeded in preparation of superconducting high entropy alloy (HEA) thin films and team from Slovak side preformed measurements of its superconducting properties. Preparation of nitride HEAs will be next step in effort to improve superconducting parameters of thin films for the purpose to be used in future quantum devices. |
| Duration: | 1.11.2023 – 31.10.2024 |
| TMQM – Ladenie frustrovaných kovových kvantových magnetov | |
| Tuning of frustrated metallic quantum magnets | |
| Program: | Inter-academic agreement |
| Project leader: | doc. RNDr. Gabáni Slavomír, PhD. |
| Duration: | 1.1.2021 – 31.12.2022 |
| Supravodivé vlastnosti tenkých vrstiev boridov | |
| Superconducting properties of boride thin films | |
| Program: | Mobility |
| Project leader: | doc. RNDr. Flachbart Karol, DrSc., akademik US Slovenska |
| Annotation: | The aim of the mobility project is to prepare thin films of superconducting borides YB6 and ZrB12, and to investigate their properties as function of thickness, microstructure and applied pressure.The outcome of this investigation will be new information about how the superconducting properties of bulk (3D) superconductors change when they become two dimensional (2D). In this regard namely a modification of superconducting properties is expected due to a considerable change of rich phonon spectra in borides and of the related electron-phonon interaction, which are responsible for the origin of superconductivity. This research on borides is unexplored, therefore new and original results are expected.The project will, moreover, enable a mutual use of laboratory equipment (for thin film preparation in Leoben, for their investigation in Kosice), it will lead to promotion of post-docs and PhD students, to preparation of common publications, and probably also to further common projects. |
| Duration: | 1.1.2021 – 31.12.2022 |
| TESTIMONIES – Teoretické a experimentálne štúdium nanomateriálov na báze oxyhydridov prechodových kovov pre supravodivosť a fotokatalýzu | |
| Theoretical and Experimental Study of Transition Metal Oxyhydride Nanomaterials for Superconductivity and Photocatalysis | |
| Program: | ERANET |
| Project leader: | doc. RNDr. Flachbart Karol, DrSc., akademik US Slovenska |
| Duration: | 1.10.2019 – 30.9.2022 |
| MGFS – Kovové geometricky frustrované systémy | |
| Metallic geometrically frustrated systems | |
| Program: | Inter-academic agreement |
| Project leader: | doc. RNDr. Gabáni Slavomír, PhD. |
| Annotation: | The principal aim of this project is to establish the microscopic anisotropy parameters and the relevant terms for the magnetic interaction in MGFS. Despite significant experimental and theoretical work, such parameters are unknown for the compounds (e.g. TmB4, HoB4) which form a Shastry Sutherland lattice (SSL) as well as for the highly symmetric face centered cubic (fcc) lattice based systems (e.g. HoB12). The experimental approach will be magnetisation measurements as a function of field direction, neutron diffraction combined with modelling techniques like WIEN2K, McPhase or SpinW. The oscillatory RKKY exchange interaction parameters are expected to be susceptible to applied pressure as well as to alloying. Suitable methods and oriented samples of rare earth borides are available.Crystal field anisotropy is theoretically described by a multipole expansion of theelectric field. The crystal field level splitting parameters will be determined frommagnetisation and specific heat data, as a function of field direction, as well as frominelastic neutron diffraction on powder samples, typically using software like McPhase.The goal of this part is a description of anisotropy of TmB4, HoB4 and the symmetric fcc– counterparts HoB12 and TmB12.The second set of parameters needed for understanding of the Hamiltonian are themagnetic interactions. They will be determined from the dispersion relationsmeasured using neutron spectroscopy on HoB4 and HoB12 along differentcrystallographic directions and in applied magnetic field. These parameters depend ondetails of the RKKY interaction which as a cross check can also be obtained from firstprinciples, using packages like WIEN2K. This type of experiments will be carried out atthe HZB Berlin on isotopically enrich Ho11B4 and Ho11B12 samples, which are availableand first testing experiments were already carried out.We intend to verify results by high pressure experiments (we assume pressuresup to 10 GPa in diamond pressure cells) which is associated with the increase ofitinerant electron concentration in MGFS, and thus with the change of parameters aswell as changes of critical fields and temperatures. This aim will cover MGFS based onthe SSL structure as well as systems based on the fcc structure. Another option to verifyresults is alloying. We will study the effect of substitution of magnetic ions like Tm3+and Ho3+ ions by nonmagnetic Lu3+ ions. Necessary devices and samples for thisresearch are available. |
| Duration: | 1.1.2019 – 31.12.2020 |
| Supravodivosť tenkých filmov boridov | |
| Superconductivity of boride thin films | |
| Program: | Bilateral – other |
| Project leader: | doc. RNDr. Flachbart Karol, DrSc., akademik US Slovenska |
| Annotation: | The aim of the proposed project is to prepare thin films of superconducting high-boron borides(YB6, ZrB12 and LuB12) and investigate their superconducting properties as function ofthickness, microstructure and of applied pressure. The outcome of this investigation will be newknowledge about how superconducting properties of bulk (3D) boride superconductors changewhen they become (quasi) two dimensional (2D). As a result, a variation of superconductingproperties is expected above all due the change of rich boride phonon spectra (and the relatedelectron-phonon interaction) when the structure changes from a 3D one to a 2D one. |
| Duration: | 1.1.2018 – 31.12.2019 |
| Magnetické vlastnosti tetraboridov | |
| Magnetic properties of tetraborides | |
| Program: | Bilateral – other |
| Project leader: | doc. RNDr. Flachbart Karol, DrSc., akademik US Slovenska |
| Duration: | 0.0.0000 – 31.12.2017 |
National
| 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 |
| LSD – Nízkorozmerné supravodivé aparáty | |
| Low-dimensional Superconducting Devices | |
| Program: | SRDA |
| Project leader: | Mgr. Szabó Pavol, CSc. |
| Annotation: | Ultralow temperatures have become an important tool for new research avenues in nanoscience, materials research and particularly in quantum nanotechnologies. Scaling down a physical system towards the sizes when the quantum properties surpass classical physics opens a plethora of new quantum-driven effects, thus giving rise to new classes of quantum materials. Within the proposed project we will focus our study on low-dimensional quantum devices, heterostrucures consisting of atomically thin superconducting slabs and aditional layers with different order (inslulator, metal, ferromagnet). In such systems symmetries can be broken possibly allowing for non trivial topological quantum states relevant for future technologies. Atomically thin layered materials are systems with zero limit bulk-to-surface ratio. Their physical properties are strongly affected by interfacing with other systems. Therefore, they represent an accessible platform for the abundance of quantum effects that can be engineered by combining them into vertical stacks using exfoliation techniques. One identifies two types of layered systems – atomically thin artificially prepared van der Waals heterostructures [Science 353, aac9439 (2016)], and naturally layered three-dimensional crystal systems. A special class of naturally layered materials is misfit structures combining alternating atomic layers of hexagonal transition metal dichalcogenides and slabs of ionic rare-earth monochalcogenides in the same superlattice [APL Mater 10, 100901 (2022)]. They feature new state of quantum matter, the Ising superconductivity resulting from broken inversion symmetry and strong spin-orbit coupling as has been recently shown by us. The misfits are also exfoliative and thus incorporable as units in vertical stacks. |
| Duration: | 1.9.2024 – 31.12.2027 |
| Magnetická frustrácia a supravodivosť v 2D a 3D boridoch | |
| Magnetic frustration and superconductivity in 2D and 3D borides | |
| Program: | VEGA |
| Project leader: | RNDr. Pristáš Gabriel, PhD. |
| Annotation: | Borides form a wide class of materials with different physical properties. Metallic geometrically frustratedmagnetic tetraborides (REB4) are 2D frustrated systems and together with their fcc 3D counterpartsdodecaborides (REB12) pose an ideal playground for study of 2D/3D interplay of frustration in megnetic systems.Uniaxial pressure, as well as hydrostatic pressure will be the tuning parameters which can change the interactionbetween magnetic moments. Depending on the direction of uniaxial pressure we will be able to change themagnitude of interactions in different crystallographic directions and test theoretical predictions. A similarcrossover between 2D and 3D can be studied also in superconducting borides as YB6, ZrB12 and LuB12. Even ifthere exist at present time a rather good understanding of the physical properties of bulk metallic borides, thereare still serious open questions what will happen if one dimension will be reduced considerably – by preparingthin films of corresponding borides. |
| Duration: | 1.1.2020 – 31.12.2023 |
| MIKROKELVIN – Kvantové materiály pri ultra-nízkych teplotách – MIKROKELVIN | |
| Quantum matters at very low temperatures – MICROKELVIN | |
| Program: | Štrukturálne fondy EÚ Výskum a inovácie |
| Project leader: | RNDr. Skyba Peter, DrSc. |
| Duration: | 1.1.2020 – 30.6.2023 |
| 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 |
| Vplyv extrémnych podmienok na silne korelované elektrónové systémy. | |
| Influence of extreme conditions on strongly correlated electron systems | |
| Program: | VEGA |
| Project leader: | doc. RNDr. Gabáni Slavomír, PhD. |
| Annotation: | Strong correlations between free (conduction) and bound (localized) electrons in a condensed matter can be change or modified by extreme conditions (very low temperatures, high pressures and magnetic fields), what often leads to the creation of new/exotic states/effects in these materials. In this proposal, we will experimentally study the newest open problems in strongly correlated electron systems (SCES), as surface conductivity in topological Kondo insulators, dynamics of frustrated antiferromagnets, Kondo vs. spin-polaron model in spin glasses, superconductivity under pressure. All this will be a very time-consuming research on new-produced samples. |
| Duration: | 1.1.2016 – 31.12.2019 |