Faculty of Physics University of Warsaw > Events > Seminars > "Modeling of Complex Systems" Seminar

"Modeling of Complex Systems" Seminar

2018/2019 | 2019/2020 | 2020/2021 | 2021/2022 | 2022/2023 | 2023/2024 | 2024/2025

room 1.40, Pasteura 5 at 15:15

Dr. Thomas Brumme (Theoretical Chemistry, TU Dresden, Germany)

Tuning the magnetic order in MPS3 via interlayer interactions

Single layers of transition-metal thiophosphates (2D-TMPS3) van der Waals magnets are an ideal platform for studying antiferromagnetic interactions in two dimensions. However, the magnetic coupling mechanism between two or more individual layers of these materials remains mostly unexplored. This study presents a density-functional based analysis and analytical models to describe the magnetic configurations of FePS3 and NiPS3 stacked bilayers. We explore the interplay between magnetic configurations and stacking shift, therefore identifying the mechanisms that result in either ferromagnetic or antiferromagnetic coupling between layers. Our findings indicate that the lowest-energy stacking is metal-dependent and that the interlayer magnetic exchange varies with both the stacking type and the metal involved. Using an Ising-Hamiltonian model and a tight-binding model based on Wannier functions, we show that interlayer exchange interactions must be considered at least up to the third nearest neighbor to elucidate the superexchange mechanism.

The seminar will be held in hybrid mode: in room 1.40 (Faculty of Physics, UW)Join Zoom Meeting:https://uw-edu-pl.zoom.us/j/94053335972?pwd=3ag9J6kMlYvbN6yJ7wmfo0G3bsaYWW.1Meeting ID: 940 5333 5972passcode: 982002

room 1.40, Pasteura 5 at 15:15

Bartosz Trzaskowski (CeNT, UW)

Computational chemistry approaches to study medium-sized and large molecular systems

In chemistry, almost everything of interest is complex, despite the very vague definition of this word. I will show how different aspects of such complexity are tackled at the Chemical and Biological Systems Simulation Laboratory of the Centre of New Technologies, University of Warsaw, by using or developing computational methods to study such diverse systems as homogeneous and heterogeneous catalysts, sensors, molecular cages and molecules, that have no practical use (yet), but are simply beautiful [1-4]. REFERENCES:[1] R. Gawin, A. Tracz, P. Krajczy, A. Kozakiewicz-Piekarz, J.P. Martinez, B. Trzaskowski, "Inhibition of the Decomposition Pathways of Ruthenium Olefin Metathesis Catalysts: Development of the Highly Efficient Catalysts for Ethenolysis", J. Am. Chem. Soc., 145, 25010-25021 (2023).[2] K.M. Bąk, B. Trzaskowski, M. Chmielewski, "Anion-templated synthesis of a switchable fluorescent[2]catenane with sulfate sensing capability", Chem. Sci., 15, 1796-1809 (2024). [3] A Serwa, A. Białońska, M. Sobieraj, J.P. Martinez, B. Trzaskowski, B. Szyszko, "Iminopyrrole-based Self-Assembly: A Route toIntrinsically Flexible Molecular Links and Knots", Angew. Chem. Int. Ed., 63, e202316489 (2024). [4] R.A. Grzelczak, T. Basak, B. Trzaskowski, V. Kinzhybalo, B. Szyszko, "Multimodal Molecular Motion in the Rotaxanes and Catenanes Incorporating Flexible Calix[n]phyrin Stations", Angew. Chem. Int.Ed., 64, e202413579 (2025).

The seminar is held in hybrid mode. Join Zoom Meeting https://uw-edu-pl.zoom.us/j/97084466352?pwd=REoPAygK6p2JyEJevuxObOry69lc6r.1 Meeting ID: 970 8446 6352 Passcode: 982002.

room 1.40, Pasteura 5 at 15:15

Dr. Przemysław Nogły (Faculty of Biochemistry, Biophysics and Biotechnology, UJ, Cracow)

Time-resolved serial crystallography to capture receptors in action

Chloride transport is an essential process maintaining ion balance across cellmembranes, cell growth, and neuronal action potentials. However, the olecular mechanism of the transport remains elusive. Among chloride transporters, light-driven rhodopsins have gained attention as optogenetic tools to manipulate neuronal signaling. We combined time-resolved serial crystallography (SwissFEL and SLS synchrotron) to provide a comprehensiveview of chloride-pumping rhodopsin's structural dynamics and molecular mechanism throughout the transport cycle from 10 ps to 50 ms [1] . We traced transient anion binding sites, obtained evidence for the mechanism of light energy utilization in transport, and identified steric and electrostatic molecular gates ensuring unidirectional transport. These structural insights provided the basis for mutagenesis and functional study of the mechanistic features enabling finely controlled chloride transport across the cell membrane.Furthermore, I will present insights into the photochemistry and selectivity of retinal isomerization in proton-pumping rhodopsin [2] and show that in favorable cases even larger structural changes can be captured in crystals [3]. Our recent study of a distinct photoreceptor, Light-Oxygen-Voltage (LOV) domain, will be introduced [4,5]. The first insights into the structural dynamics of LOV photoactivation will be presented, providing the basis for proposing a molecular mechanism of a covalent thioether bond formation between a flavin mononucleotide cofactor and a reactive cysteine, Cys57 (unpublished).References: [1] Mous, S. et al. Science 375 (2022) 845.[2] Nogly P et al., Science 361 (2018), eaat0094.[3] Weinert et. al., Science 365 (2019), 61.[4] Gotthard et al. IUCrJ (2024), 749.[5] Gotthard et al. IUCrJ (2024), 792.

The seminar is held in hybrid mode. Join Zoom Meeting https://uw-edu-pl.zoom.us/j/97084466352?pwd=REoPAygK6p2JyEJevuxObOry69lc6r.1 Meeting ID: 970 8446 6352 Passcode: 982002

room 1.40, Pasteura 5 at 15:15

Dr. Sławomir Prucnal (HZDR, Dresden, Germany)

Non-equilibrium thermal processing of solids

Most of the scientists or users have a pragmatic approach to ms-range flash lamp annealing as a valuable tool. However, FLA differs in several aspects from conventional annealing like furnace or rapid thermal annealing which sometimes gives rise to unexpected results: (1) it is not performed in thermal equilibrium, (2) there are steep temperature gradients, (3) the resulting temperature profile strongly depends on the material system, and, (4) temperature measurement is challenging due to the very short processing times. However, the non-equilibrium approach has several advantages: it allows the treatment of temperature-sensible substrates, it allows specific dynamic processes like explosive crystallization or hyperdoping, and it suppresses unwanted processes like diffusion or segregation. In addition, it saves energy, costs and process times, and it is suitable for roll-to-roll applications. The the lecture will provide an overview of the most common applications of the FLA in semiconductor technology starting with silicon through metal oxides to monolayer thick van der Waals crystals.

The seminar is held in hybrid mode. Join Zoom Meeting https://uw-edu-pl.zoom.us/j/97084466352?pwd=REoPAygK6p2JyEJevuxObOry69lc6r.1 Meeting ID: 970 8446 6352 Passcode: 982002

room 1.40, Pasteura 5 at 15:15

Dr. Maciej Marchwiany (ICM, UW)

The Application of Artificial Intelligence in Natural Sciences

Artificial Intelligence (AI) has become a widely used tool in scientific work. AI not only enables advanced data analysis and visualization, but it can also be used to speed up numerical simulations by approximation of potentials or even replacing traditional simulations. Moreover, AI allows for quick searching of scientific publication databases and generating article summaries or information extraction. Additionally, AI and generative models are used more frequently for the comprehensive writing of scientific papers. During the talk I will introduce key concepts of artificial intelligence and machine learning. I will present the applications of AI in science and the opportunities these tools offer to researchers. Finally, I will talk about the latest trends and the most interesting scientific projects involving the use of artificial intelligence.

The seminar will be held in hybrid mode: in room 1.40 (Faculty of Physics, UW) Join Zoom Meeting: https://uw-edu-pl.zoom.us/j/97084466352?pwd=REoPAygK6p2JyEJevuxObOry69lc6r.1 Meeting ID: 970 8446 6352, Passcode: 982002

join us at 15:15

Dr. Andrea Leon (Physics Department, Faculty of Sciences, University of Chile)

(online) Tuning altermagnetic phases in Ca3Ru2O7 under strain

online - ZOOM

Ca3Ru2O7 is an antiferromagnetic (AFM) polar metal considered a fascinating material due to its wide range of remarkable electronic phenomena, including colossal magnetoresistance, spin waves, and multiple phase transitions. Exploring these properties under external manipulation, such as electrical current, pressure, or strain, opens new pathways for understanding its electronic behavior and controlling its quantum states. In this study, we employ ab initio methods to investigate the stability of several AFM configurations of Ca3Ru2O7 under lattice deformation (pressure and strain). We identify potential altermagnetic (AM) states, a recently discovered elemental magnetic phase, and show that these states can be stabilized under strain. We discussthe underlying mechanisms responsible for the stability of the AM phase and propose a novel route for tuning quantum states through AFM to AM transitions in Ca3Ru2O7 under lattice deformation. Tuning magnetic phases from AFM-metal (ground state) to AM-insulator under strain.

This seminar will be held online via Zoom platform: https://uw-edu-pl.zoom.us/j/97084466352?pwd=REoPAygK6p2JyEJevuxObOry69lc6r.1 Identyfikator spotkania: 970 8446 6352 Kod dostępu: 982002

room 1.40, Pasteura 5 at 15:15

Dr. Thomas Brumme (Theoretical Chemistry, TU Dresden, Germany)

The whole is more than the sum of its parts: electron-phonon and exciton-phonon coupling in layered materials

Scientists are uncovering fascinating ways in which light interacts with electrons and vibrations in ultra-thin layers of special materials called transition metal dichalcogenides. When exposed to light, electrons in these materials get "excited" and begin to transfer energy to the atoms around them. This process, involving vibrations known as phonons, is key to controlling how these materials conduct heat and electricity, which could make them valuable for next-gen electronics. Combining femtosecond electron diffraction experiments with our theoretical calculations, we studied in WSe2 how excited electrons distribute their energy across different phonons. We found that this energy transfer is not uniform; it varies with momentum and initially creates an uneven, “non-thermal” phonon distribution. Over time, however, this distribution evens out, leading to a stable, thermal state.Going further, we studied more recently the interaction between WSe2 and MoSe2 when stacked together in a layered structure. Here, we observed a strong interlayer connection: phonons in one layer influence excitations (excitons) in the other. Using Raman scattering techniques together with density-functional calculations, we show that MoSe2 vibrations couple stronger to WSe2 excitons than vice versa, highlighting a unique coupling effect that cannot be understood by looking at either layer alone.Instead, it is the interaction between layers that creates new electronic and vibrational behaviors. These findings might help to develop finely-tuned, light-responsive materials with applications in optoelectronics and quantum technologies.

The seminar is held in hybrid mode:Join Zoom Meetinghttps://uw-edu-pl.zoom.us/j/97084466352?pwd=REoPAygK6p2JyEJevuxObOry69lc6r.1Meeting ID: 970 8446 6352Passcode: 982002

room 1.40, Pasteura 5 at 15:15

Stanisław Żukowski (IFT UW)

Breakthrough-Induced Loop Formation in Evolving Transport Networks

ransport networks, such as jellyfish canal network or river networks, provide key functions in organisms and the environment. They usually contain loops whose significance for the stability and robustness of the network is well documented. However, the dynamics of their formation is usually not considered. Such structures often grow in response to the gradient of an external field. During evolution, extending branches compete for the available flux of the field, which leads to effective repulsion between them and screening of the shorter ones. Yet, in remarkably diverse processes, from the canal system of jellyfish to unstable fluid flows, loops suddenly form near the breakthrough when the longest branch reaches the boundary of the system. We provide a physical explanation for this universal behavior. Using a 1D model, we explain that the appearance of effective attractive forces results from the field drop inside the leading finger as it approaches the outlet. Furthermore, we numerically study the interactions between two fingers, including screening in the system and its disappearance near the breakthrough. Finally, we perform simulations of the temporal evolution of the fingers to show how revival and attraction to the longest finger leads to dynamic loop formation. We compare the simulations to the experiments and find that the dynamics of the shorter finger are well reproduced. Our results demonstrate that reconnection is a prevalent phenomenon in systems driven by diffusive fluxes, occurring both when the ratio of the mobility inside the growing structure to the mobility outside is low and near the breakthrough.

The seminar will be held in hybrid mode, join Zoom Meeting, https://uw-edu-pl.zoom.us/j/97084466352?pwd=REoPAygK6p2JyEJevuxObOry69lc6r.1Meeting ID: 970 8446 6352 Passcode: 982002

room 1.40, Pasteura 5 at 15:15

Carmine Autieri (MagTop IF PAN)

Spin-orbital properties of the altermagnets

The Dzyaloshinskii-Moriya interaction (DMI) has explained successfully the weak ferromagnetism in some centrosymmetric antiferromagnets. However, in the last years, it was generally claimed that the DMI is not effective in such systems. We reconciled these views by separating the conventionalantiferromagnets from altermagnets. Altermagnets are collinear magnets having zero magnetization preserved by crystal symmetries in the non-relativistic limit. The spin-up and spin-down sublattices are connected by rotation (proper or improper and symmorphic or nonsymmorphic). Consequently, the system shows even-parity wave spin order in the k-space lifting the Kramer’s degeneracy in the non-relativistic band structure leading to unconventional magnetism. The staggered DMI is one ofthe mechanisms that can create weak ferromagnetism or weak ferrimagnetism in centrosymmetric and noncentrosymmetric altermagnets while it is not effective in conventional antiferromagnets.Once the spin-orbit coupling is included in an altermagnetic system (where the time-reversal symmetry is broken) with staggered DMI, the components of spin moments of the two sublattices alongthe N´eel vector are antiparallel but the other two spin components orthogonal to the N´eel vector can be null, parallel or antiparallel. In cases where we have different bands showing parallel and antiparallel spin components at the same time, the magnetic order results in weak ferrimagnetism. The altermagnetic compounds can host weak ferromagnetism, weak ferrimagnetism or zero magnetization. Restricted to the altermagnet with 2 atoms and staggered DMI, the Hall vector is orthogonalto the N´eel vector in the case of weak ferromagnetism and weak ferrimagnetism with a magnetic component proportional to the DMI. We find a sign change of the magnetization, and possibly of theanomalous Hall effect, as a function of the band filling and N´eel vector. We describe the dependence of the weak ferromagnetism on the charge doping.

The seminar is held in hybrid mode:Join Zoom Meetinghttps://uw-edu-pl.zoom.us/j/97084466352?pwd=REoPAygK6p2JyEJevuxObOry69lc6r.1Meeting ID: 970 8446 6352Passcode: 982002

room 1.40, Pasteura 5 at 15:15

Tomasz Woźniak (IFT UW)

Excitonic g-factors in van der Waals structures

The shifts of optical peaks energies under external magnetic field, quantified by effective g-factors, provide a deep insight into electronic and excitonic structures of two-dimensional materials. A recently developed first-principles-based method for calculation of g-factors, including bands-summation formula, yields excellent agreement with experiments for intralayer excitons in monolayer (1L) transition metal dichalcogenides (TMDCs), interlayer excitons in TMDCs heterobilayers, as well as larger excitonic complexes in doped 1L TMDCs [1,2]. The last case corroborates the accuracy of the method for evaluation of single bands g-factors. Here we present more advanced cases which are beyond the possibilities of simplistic models with spin, atomic orbital and valley contributions. We explain the reduction of g-factors measured in MoSe2/WS2 moiré heterobilayer by inclusion of exciton g-factor’s dispersion and spatial confinement in moiré potential [3]. Inclusion of excitonic wavefunctions calculated by model Bethe-Salpeter equation enables us to understand the measured excitonic state dependence of g-factors in 1L and homobilayer TMDCs [4,5]. We analyze the influence of biaxial strain on 1L TMDs, finding a large strain dependence of excitonic g-factors, with significant spin-mixing effects [6]. The calculated trends of direct and indirect excitons g-factors in WS2 micro-bubbles allow us to explain the strain-induced exciton hybridization in WS2 monolayers unveiled by magnetooptical measurements [7]. We investigate a new class of hexagonal 2D materials with formula MSi2Z4 (M: Mo, W; Z: N, P, As, Sb), which are isosymmetric to 1L TMDCs. We find a new set of circularly polarized excitonic transitions with high binding energies and large positive g-factors [8].[1] Phys. Rev. B 101, 235408 (2020).[2] Nano Lett. 21, 2519 (2021).[3] Nano Lett. 22, 8641 (2022).[4] Nano Lett. 19, 2464 (2019).[5] 2D Mater. 10, 025014 (2023).[6] New J. Phys. 24, 083004 (2022).[7] Phys. Rev. Lett. 129, 067402 (2022).[8] Small 19 2206444 (2023).

The seminar will be held in hybrid mode: in room 1.40 (Faculty of Physics, UW). Join Zoom Meeting https://uw-edu-pl.zoom.us/j/97084466352?pwd=REoPAygK6p2JyEJevuxObOry69lc6r.1 Meeting ID: 970 8446 6352 Passcode: 982002