Theoretical physics of condensed matter is one of the most progressive parts of modern physics. The wealth of systems studied by condensed matter physics provides opportunities for fascinating physical phenomena and open new ways for technological innovations.
Classical phase transitions (e.g. evaporation) are commonly encountered in extended thermodynamic systems. Intriguingly, quantum mechanics offers ways to engineer so called quantum phase transitions in tiny conducting islands called quantum dots, which are attached to superconducting electrodes.
Kadlecová, M. Žonda, V. Pokorný and T. Novotný,
Practical guide to quantum phase transitions in quantum-dot-based tunable Josephson junctions,
Physical Review Applied 11, 044094 (2019)
Topological and 2D materials
With advent of new materials and technologies the quatum-relativistic effects in condesed matter have become more important. An important manifestation of relativistic behaviour in condensed matter is coupling of spin and orbital momenta, called spin-orbit interaction. The latter drives certain materials through a topological transition.
- Šebesta J., Carva K., Kriegner
D., Honolka J.,
Twin Domain Structure in Magnetically Doped Bi2Se3 Topological Insulator,
Nanomaterials 10, 2059 (2020).
Topological effects manifest especially strongly in 2D materials. Their research was pioneered by the invention of graphene and since then keeps gaining importance. In our group we focus on their optical properties and quantum transport.
Can you envision minimizing the elements of electronics down to the scale of single tiny molecules? Researchers from physics, chemistry and meterials sciences have joined efforts to fabricate, measure and understand so called molecular junctions. Their electronic properties like the IV curve are entirely governed by quantum effects, e.g. quantum interference and tunneling. The wealth of experiments calls for developing applicable quantum transport theories. Read more in our large review paper:
- F. Evers, R. Korytár, S. Tewari, J.
M. van Ruitenbeek,
Advances and challenges in single-molecule electron transport,
Reviews of Modern Physics 92, 035001 (2020)
Development of new methods and Machine Learning
To study the problems of condensed matter physics, we use both paper-and-pencil theory as well as numerical calculations. For studying the basic physical features of materials with atomistic input we use ab initio and multiscale approaches. In recent years, we have adopted machine learning for the investigation of complex condensed matter systems.
- J. Arnold, F. Schäfer, M. Žonda and A. U. J. Lode,
Interpretable and unsupervised phase classification,
Phys. Rev. Research 3, 033052, (2021)
The progress in optics allows nowadays to generate femtosecond laser pulses with wavelengths ranging from the terahertz to the x-ray regime. Such pulses can record “movies” of extremely fast processes in magnetic materials. Our department takes part in this fascinating development theories by developing theories that predict and interpret this novel phenomenology.
- Slobodeniuk, A. O., Koutenský,
P., Bartoš, M., Trojánek, F., Malý, P., Novotný, T., & Kozák, M.
Ultrafast valley-selective coherent optical manipulation with excitons in WSe2 and MoS2 monolayers
npj 2D Materials and Applications, 7(1), 17 (2023).
Computational design of new devices
For novel technological applications, we study magnetotransport through multilayer structures consisting of alternating magnetic and non-magnetic layers. These structures are well known for a possibility of manipulating their magnetizations by means of spin transfer torque. The effect of spin transfer torque can potentially control magnetic random access memories.
- Ritzmann, U., Baláž, P., Maldonado, P., Carva,
K., & Oppeneer, P. M.
High-frequency magnon excitation due to femtosecond spin-transfer torques.
Physical Review B, 101(17), 174427 (2020)