Phd Disertation Themes

Institute of Physics offers several PhD positions every year in a few doctoral degree programs. Possible topics for Your study can be found below. As a first step, it is best to contact the potential supervisor who will provide you with the most qualified answers to the topic, tasks and position requirements.

Study year 2024/25

  1. Study program:
    Theoretical and Mathematical Physics / FMFI UK
    Annotation:
    Tensor Network represents a modern mathematical tool that can accurately describe quantum states. We focus on the description of strongly correlated spin (magnetic) systems. A quantum tensor-product state represents the tensor network. It carries physical degrees of freedom which are interconnected via auxiliary (non-physical) degrees of freedom controlling correlations and quantum entanglement. During the PhD studies, we will analyze non-trivial topological phases by the quantum entanglement entropy, concurrence, negativity, and standard observables. Since these spin systems are not exactly solvable, we will develop novel numerical procedures using any preferable programming language (e.g., Python, Julia, C++, etc.) The goal is to propose alternative methods of tensor networks originating in renormalization-group techniques. We also intend to analyze hyperbolic curved lattices to revisit quantum gravity from a different viewpoint.
    Contact: andrej.gendiar@savba.sk
  2. Study program:
    Theoretical and Mathematical Physics / FMFI UK
    Annotation:
    NISQ (Noisy intermediate-scale quantum) computers are quantum computers available today that contain tens to a few hundred qubits, can execute a protocol with a depth of a few tens of steps, and are heavily influenced by errors and noise. We will develop and test algorithms applicable on such computers.
    Contact: martin.plesch@savba.sk
  3. Study program:
    Theoretical and Mathematical Physics / FMFI UK
    Annotation:
    Current stage of development of quantum computers is termed as Noisy intermediate-scale quantum (NISQ) era. Capabilities of such devices are quite limited with respect to quality and quantity of the qubits, performed gates or types of measurements. Thus, to fully unlock their potential implemented tasks should be carefully optimized with respect to usage of those resources. The goal of the student will be to learn and further develop methods for optimization of higher order maps with chosen resource and causal structure. The student should also work with and improve methods for finding quantum circuit implementations of such optimal maps and other known or newly developed quantum information processing tasks. The research goals are planned to be addressed mostly by analytical means, but also computer assisted approach can be envisioned and would be welcomed.
    Contact: michal.sedlak@savba.sk
  4. Study program:
    Theoretical and Mathematical Physics / FMFI UK
    Annotation:
    Critical reconsideration on assumptions on the interpretation of recorded data and certification of quantum features. The precise problem formulation depends on the preferences of PhD student. The subject includes area of device-independent protocols, quantum memory channels, quantum network theory, direct estimation protocols and higher-order quantum structures.
    Contact: mario.ziman@savba.sk
  5. Study program:
    Theoretical and Mathematical Physics / FMFI UK
    Annotation:
    Quantum communication infrastructures are under intensive construction. Even if not fully functional yet they open several interesting theoretical challenges and opportunities. Our goal is to contribute to their theoretical development by investigating the efficiency and robustness of quantum communication protocols, and design novel network protocols and algorithms. The particular research task will depend on preferences of the student.
    Contact: mario.ziman@savba.sk
  6. Study program:
    Theoretical and Mathematical Physics / FMFI UK
    Annotation:
    The circuit model of quantum computation is based on unitary gate decomposition, however, it is not necessary to perform the full unitary transformation in order to evaluate a function f. Our goal is to explore the possibility of using noisy gates to accomplish this task.
    Contact: mario.ziman@savba.sk
  7. Study program:
    Physics of Condensed Matter and Acoustics / FMFI UK
    Annotation:
    Experimentally known phase may or may not be in state of thermodynamic equilibrium, their apparent “stability” may be just a consequence of kinetically blocked transformation to a hypothetical truly stable phase. Similarly, variation of kinetic circumstances during alloy-compound formation may lead to formation of so far unknown metastable structure with possibly distinct physical properties compared with the previously known compound structure. By controlling circumstances furing phase formation during atomistic simulations based on density functional and machine learning, we will screen existence of so far unknown minima of potential energy for series of candidate chemical compositions.
    Contact: marek.mihalkovic@savba.sk
  8. Study program:
    Physics of Condensed Matter and Acoustics / FMFI UK
    Annotation:
    Focus of the thesis is preparation and implementation of the concept of substitution of existing equilibrium Wyckoff crystallographic positions in known equilibrium crystalline lattice by different types of majority metal atoms consisting of a set of 3-5 additional/other suitable atoms. These atoms, so-called HEA atoms, will be selected in accordance with the principle of High Entropy Alloys (HEA) or compounds e.g. ceramics, dielectrics or oxides, to form a similar, mutually shared crystallographic structure with lattice parameters comparable to those of the original equilibrium unit cell and are inserted for the purpose of controlled optimization of physical properties of the system. Objects of application of such concept will be alloys derived from classical known HEA but also systems forming metallic glasses of metal-metalloid type, porous catalytic materials, selected ceramics based on carbides and borides or oxides, using possibility to prepare systems in non-equilibrium state via different cooling rates.
    Contact: peter-svec@savba.sk
  9. Study program:
    Physics of Condensed Matter and Acoustics / FMFI UK
    Annotation:
    Establishment of microstructural-magnetic correlation and identification of processing parameters governing the formation of hard magnetic phases. Development of preparation and processing routes for maximization of the figure of merit via fine composition tuning, refinement of processing and structural evolution of hard magnetic phases . Detailed microstructural and thermodynamic analysis using cutting edge methods and techniques.
    Contact: peter-svec@savba.sk
  10. Study program:
    Physics of Condensed Matter and Acoustics / FMFI UK
    Annotation:
    The PhD candidate will focus on the modeling of crystal structures using a modern numeric technique based on the atomic approach and the fundamental principles of quantum mechanics. The primary method for these simulations will be Density Functional Theory (DFT), which allows for the efficient solution of complex quantum mechanical problems of many-electron systems, such as are represented by a real condensed matter. The work will focus on simulations of lattice dynamics- the phonon system, and its interaction with the electronic system. Based on this, it will be possible to predict, within the quasi-harmonic approximation, the region of dynamic stability, thermodynamic properties (e.g., thermal expansion), and the influence of thermal vibrations of the crystal on its electronic properties depending on the thermodynamic temperature and external pressure. The computationally obtained data will be compared with experimental measurements of optical absorption and photoluminescence, respectively, or to interpret real experiments. The considered substances under investigation will be perovskite structures grown in the form of films/nanostructures containing heavy metals (Pb, Cs) and halides (Cl, Br, I), which are suitable as light absorption layers in a new class of photovoltaic cells.
    Contact: kamil.tokar@savba.sk
  11. Study program:
    Nuclear and Subnuclear Physics / FMFI UK
    Annotation:
    Experiment 22.76 was performed at LNL INFN in Legnaro, Italy, with the goal of studying transition probabilities of low-lying excited states in isotopes near the N = 126 closed shell through lifetime measurements. These states were populated via a multi-nucleon transfer reaction, where a 136Xe beam impinged on a self-supporting 198Pt target, resulting in data collection for a wide range of W–Pb isotopes. Gamma rays were detected using AGATA, one of the most advanced gamma-ray tracking detector arrays in the world, coupled with the PRISMA large-acceptance magnetic spectrometer for complete identification of beam-like ions. Both spectrometers were positioned based on the grazing angle of the reaction. A dedicated plunger device, used in a reversed configuration, was employed for lifetime measurements. A Nb foil acted as the stopper/degrader, stopping target-like particles and allowing for the observation of the ratio between stopped and in-flight emitted gamma rays. Due to the complexity of this modern experimental setup, data analysis is particularly challenging, and the results are frequently compared with dedicated simulations.
    References:
    [1] Rowe, D. J. (2010). Nuclear Collective Motion: Models and Theory. Singapore: World Scientific Publishing Company. ISBN: 978-981-279-065-1. [2] Rowe, D. J., Wood, J. L. (2010). Fundamentals of Nuclear Models: Foundational Models. World Scientific Publishing Company. ISBN: 978-9812569561. [3] Jenkins, D., Wood, J. L. (2023). Nuclear Data: A collective motion view. IOP Publishing Company. ISBN: 978-0-7503-5641-1.
    Contact: andrej.herzan@savba.sk
  12. Study program:
    Nuclear and Subnuclear Physics / FMFI UK
    Annotation:
    The presented topic is part of a very successful research program focused on the study of neutron-deficient odd-mass gold isotopes and phenomena such as shape coexistence, evolution of nuclear deformation etc. For a deeper understanding and the ability to compare experimental data with theoretical models, it is necessary to know the reduced transition probabilities of electromagnetic transitions in nuclei, which directly enter the nuclear matrix elements - carriers of information about the nuclear structure. For this purpose, the research group from the Department of Nuclear Physics of the Institute of Physics of the Slovak Academy of Sciences carried out a 2-week experiment (code name: JR166) at the Accelerator Laboratory of the University of Jyväskylä (JYFL) in Finland. The student's task will be the analysis and physical interpretation of the data from the JR166 experiment. The student will also be involved in the activities of the research group in laboratories abroad: JYFL (Finland), CERN-ISOLDE (Switzerland), INFN-LNL Legnaro (Italy). A presentation of results at international conferences and workshops is as well expected. Knowledge of English is therefore desirable. The topic is part of the active research grants, which guarantees continuous funding.
    References:
    1. D. J. Rowe, J. L. Wood, Fundamentals of nuclear models: foundational models, WSPC (2010), ISBN-13: 978-9812569554. 2. D. Jenkins, J. L. Wood, Nuclear Data: A primer, IOP Publishing (2021), ISBN-13:‎ 978-0750326728. 3. D. Jenkins, J. L. Wood, Nuclear Data: A collective motion view, IOP Publishing Ltd (2023), ISBN: 978-0-7503-5643-5. 4. K. Heyde, Basic ideas and concepts in nuclear physics, IOP Publishing Ltd (2004), ISBN: 0-7503-0980-6. 5. J. Suhonen, From nucleons to nucleus, Springer (2007), ISBN-13: 978-3-540-48859-0.
    Contact: andrej.herzan@savba.sk
  13. Study program:
    Nuclear and Subnuclear Physics / FMFI UK
    Annotation:
    The mean-field methods, based on Skyrme or Gogny functional, or the relativistic mean-field, belong among the standard tools for the microscopic description of atomic nuclei along the whole chart of nuclides. However, most of the existing nuclei have open-shell configuration, where the nucleon-nucleon pairing becomes an important phenomenon which needs to be addressed. Usual treatments involve the BCS approximation, or some of its enhancements, such as HFB (Hartree-Fock-Bogoliubov), projected BCS, or Lipkin-Nogami scheme [1,2]. There are certain unsatisfactory aspects in most of these methods, such as energy cut-off [3], the different interaction employed for the mean-field and the pairing contribution, and the appearance of spurious contributions in the excitation spectra [4]. There exist also some alternative approaches for the treatment of short-range correlations, such as seniority, quartet pairing [5], or Brückner-Hartree-Fock. The task of the doctoral student will consist in active participation in the development of computer codes based on Hartree-Fock, implementation of some of the approaches mentioned above, evaluation of their accuracy, and their possible improvements. For this aim, a working knowledge of C programming is required. Knowledge of additional frameworks, such as C++, Rust, CUDA or OpenCL is also welcome.
    References:
    [1] P. Ring and P. Schuck, The Nuclear Many-Body Problem (Springer-Verlag, Berlin, 1980). [2] M. Bender, P.-H. Heenen, and P.-G. Reinhard, Rev. Mod. Phys. 75, 121-180 (2003). [3] M. Bender, K. Rutz, P.-G. Reinhard, and J.A. Maruhn, Eur. Phys. J. A 8, 59-75 (2000). [4] J. Kvasil, A. Repko, and V.O. Nesterenko, Eur. Phys. J. A 55, 213 (2019). [5] D. Negrea and N. Sandulescu, Phys. Rev. C 90, 024322 (2014).
    Contact: anton.repko@savba.sk
  14. Study program:
    Nuclear and Subnuclear Physics / FMFI UK
    Annotation:
    The formation of positronium in polymer networks of selected model materials from the group of methacrylates and epoxides will be investigated in in-situ experiments at high pressures in the range of 0-700 MPa. The local free volume is strongly dependent on the dynamics of polymer chains as well as segmental motion, i.e. on the temperature and pressure applied to the polymer volume or on the polymer composition itself. The local free volume will be studied using a positronium probe and measuring its lifetime at the annihilation site by the positron annihilation time spectroscopy (PALS) technique. The source of positrons will be the radioisotope 22Na. Based on the experimentally obtained data by the PALS technique and suitable models for converting orthopositronium lifetimes to the size of free volume cavities, the properties of the studied network, such as compressibility, will be characterized. The results will be compared with the characteristics obtained using other techniques, such as IR spectroscopy. The effect of high pressures on the formation of Ps is not entirely clear, original results are expected.
    Contact: ondrej.sausa@savba.sk
  15. Study program:
    Nuclear Chemistry and Radioecology / PRIF UK
    Annotation:
    Using a positronium probe and the positron annihilation lifetime spectroscopy (PALS) technique, changes in local free volume during the photopolymerization process in selected types of materials (based on dimethacrylates, acrylated epoxidized soybean oils, etc.) will be investigated. Their networks and reaction conditions will be modified to achieve the desired values ​​of microshrinkage of the polymer network. High shrinkage is not suitable for many applications, as it causes internal stress in the materials with consequences for their material properties. This is important, for example, for materials for 3D printing or for dental materials. Local free volume in polymers will be determined from measurements of orthopositronium lifetimes. The radioisotope 22Na will be used as the positron source. Microstructural properties obtained by PALS measurements will be compared with other network properties investigated by techniques such as Electron Paramagnetic Resonance and Infrared Spectroscopy.
    Contact: ondrej.sausa@savba.sk
  16. Study program:
    Quantum Electronics, Optics and Optical Spectroscopy / FMFI UK
    Annotation:
    The goal of this thesis work will be to leverage quantum resources that came available to experimentalists since the second quantum revolution to either investigate and better understand fundamental concepts of the quantum theory or demonstrate potentially new applications for future quantum technologies. This work will be achieved through the realization of several photonic-based experimental setups: single photon sources, generation of entanglement, spectroscopy-based stabilization schemes for feedback loop and more.
    Contact: djeylan.aktas@savba.sk
  17. Study program:
    Quantum Electronics, Optics and Optical Spectroscopy / FMFI UK
    Annotation:
    Next-generation solid-state batteries (SSBs) have the potential to transform the field of electromobility, offering enhanced safety and increased energy density. However, the successful realisation of this potential is contingent upon a more profound comprehension of the redox reactions occurring within SSBs. This enhanced knowledge is imperative for enhancing the cyclability of these batteries. The present project aims to develop an operando setup utilising wide-angle X-ray scattering (WAXS) for real-time analysis of these reactions during battery cycling under laboratory conditions.The project will utilise state-of-the-art high-brilliance laboratory microfocus X-ray sources (Ag Ka) and CdTe 2D X-ray detectors. These experiments will be performed in collaboration with the HORIZON EU projects, OPERA and SEATBELT, thereby guaranteeing involvement in a highly motivated international research team.
    References:
    1. Jürgen Janek and Wolfgang G. Zeier, “Challenges in Speeding up Solid-State Battery Development,” Nature Energy 2023 8:3 8, 230–40, https://doi.org/10.1038/s41560-023-01208-9.
    Contact: karol.vegso@savba.sk
  18. Study program:
    Physcial Engineering / FEI STU
    Annotation:
    The theme of doctoral work is to investigate the transport of the heat of natural wooden materials and their composites. Wood -based composites glued by polymer materials belong to the class of sustainable insulating materials with the potential of use in wooden buildings. Good thermal insulation properties predestine them for use in harsh climatic conditions. The effectiveness of their use in real climatic conditions depends on many parameters. The transport of heat in such materials is multi-parametric because it is a simultaneous heat transfer through the components of the structure. Experimentally, transient non-stationary thermophysical methods, specifically a pulse and step-wise transient method and a plane hot disk method, will be used. One task will be to determine thermophysical parameters of anisotropic materials for different directions of their structure. Another task is to assess the suitability of physical and numerical models for heat transport models in an inhomogeneous structure with different geometry of wood filler particles. The results obtained by the numerical model will be compared to the data obtained by experimental methods.
    Contact: vlastimil.bohac@savba.sk
  19. Study program:
    Physcial Engineering / FEI STU
    Annotation:
    The characterization of the thermal properties of materials is the basic condition of their use in conjunction with their use in real conditions. Recently, we have noticed an increase in the number of non-stationary measuring methods based on the principle of dynamic temperature change. The transitional or dynamic methods use non-stationary temperature fields to characterize thermal transport and material parameters. Usually, the thermal response to the heat pulse generated by the heat source is monitored. The thermal response is registered out in two ways. Either at a certain distance from the heat source of the pulse or at the source/sensor site. Accordingly, we divide sensors into two-probe where the temperature is sensed by a thermocouple located outside the heat source and in the case of single-probe sensors, the temperature response is sensed by the heating element itself. So the thermal response to the heat disturbance in a form of the pulse or step-wise form of heat is scanned by a thermocouple located apart of the heat source, or by sensor that is the heater and thermometer in the same time. By applying the appropriate physical model, the thermal response parameters are sought by minimizing the parameters of thermal diffusivity and thermal conductivity and volume thermal capacity or specific heat capacity. The use of one-probe sensors and the development of methods and measuring instruments to investigate the thermal properties of materials is therefore an interesting and necessary step to improve experimental measuring techniques. The results of development of single-probe sensors and methods as well as construction of new measuring electronics will enable more efficient and applied research to solve the problem of heat transport problems for a wide range of new technologically interesting materials even in various industries industry.
    Contact: vlastimil.bohac@savba.sk

PhD themes

  • Study year 2024/25 / CSV
  • Study year 2023/24 / CSV