У оквиру семинара Центра за изучавање комплексних система Института за физику у Београду, а у оквиру пројекта Polaron Mobility in Model Systems and Real Materials (PolMoReMa), у четвртак, 27. новембра 2025. године у 14 часова у читаоници библиотеке „Др Драган Поповић“, Сузана Миладић (Лабораторија за примену рачунара у науци, Институт за физику у Београду) одржаће предавање:

QMC study of transport in Holstein polaron model

САЖЕТАК:

Organic semiconductors are emerging materials that are shaping modern technologies (OLEDs, OFETs, OPVs). Their low cost, mechanical flexibility, and tunable properties make them highly promising for a
wide range of applications. However, realizing their full potential requires a detailed understanding of charge transport in these materials.

In this work, we investigate transport within the Holstein polaron model—a simple yet representative framework for organic molecular semiconductors. We develop a path-integral Quantum Monte Carlo method for computing current–current correlation functions and the dc mobility in the 1D Holstein model [1]. By carefully choosing the basis for the trace expansion in path integral, we suppress the dynamical sign problem and are able to evaluate correlation functions over long real-time intervals with small errors.

Using the Kubo formula, we extract the dc mobility either through direct integration of real-time correlation functions or via analytic continuation that combines real- and imaginary-time data. This approach yields highly precise results for dc mobility across a broad parameter range. The numerically exact results obtained here provide a great benchmark for evaluating the validity of commonly used transport theories, which rely on approximations appropriate only in extreme cases (strong or weak electron–phonon coupling, very low or high temperature).

By comparing our numerical results to the predictions of each transport theory, we are able to map out the parameter ranges—defined by temperature, electron–phonon interaction strength, and phonon frequency—over which small-polaron hopping, polaron band transport, or conventional band transport offers an accurate description of charge transport. This allows us to construct a transport-regime diagram for the 1D Holstein model, offering better insights into its transport behavior [2].

This research is supported by the Science Fund of the Republic of Serbia, Grant No. 5468, Polaron Mobility in Model Systems and Real Materials – PolMoReMa.

[1] S. Miladić and N. Vukmirović, Phys. Rev. B 107, 184315 (2023).
[2] S. Miladić and N. Vukmirović, Phys. Rev. B 112, 054314 (2025).

У оквиру семинара „Историја науке и епистемологија“, а поводом стогодишњице настанка квантне механике, у уторак, 25. новембра 2025. године у 13 часова у читаоници библиотеке „Др Драган Поповић“, др Игор Салом (Институт за физику у Београду) одржаће предавање:

Парадокс Вигнеровог пријатеља

У оквиру семинара Групе за гравитацију, честице и поља, у петак, 21. новембра 2025. године у 11:15 у сали 360 Института за физику у Београду, др Игор Прлина (Институт за физику у Београду) одржаће предавање:

Decoherence Limits on Weak-Value Amplification and Their Implications for Low-Energy Probes of High-Energy Physics

САЖЕТАК:

Weak measurements with postselection allow amplification of signals relative to noise far beyond what standard measurements can achieve. In principle, arbitrarily large weak-value amplification could reveal signatures of high-energy physics even in low-energy experiments, provided that sufficiently large ensembles are available. However, this is no longer the case once decoherence is taken into account. In this talk I discuss how decoherence, viewed as an effective non-unitary evolution, limits the achievable weak-value amplification. I analyze a simple thermal decoherence model and apply it to two systems of practical interest: an electron in a magnetic field and a harmonic oscillator. This analysis has a use on its own: the resulting expressions provide approximate methods for extracting decoherence rates from weak-measurement data and for estimating corrections to weak measurement experimental results for which decoherence was originally neglected. Finally, I outline a speculative implication: if weak-value amplification could in principle access high-energy physics at low energies, then decoherence may act as a natural protection mechanism. This motivates the possibility that quantum gravity itself induces fundamental decoherence, preventing low-energy experiments from probing high-energy behavior.

У оквиру семинара Центра за изучавање комплексних система Института за физику у Београду, у четвртак, 20. новембра 2025. године у 14 часова у читаоници библиотеке „Др Драган Поповић“, др Ана Худомал (Институт за физику у Београду) одржаће предавање:

Escaping Thermalization: Quantum Simulations of Many-Body Scars

САЖЕТАК:

Understanding thermalization in isolated quantum systems is one of the central challenges in quantum many-body physics. While the eigenstate thermalization hypothesis provides a general framework, an increasing number of exceptions are now known. One such exception is a novel class of systems in which a small number of non-thermal eigenstates coexist with an otherwise ergodic spectrum, representing a form of weak ergodicity breaking [1]. These atypical eigenstates, known as quantum many-body scars (QMBS), can lead to unexpectedly long-lived coherent dynamics. In this talk, I will discuss how QMBS behavior can be realized and explored using a variety of quantum simulators, including Rydberg-atom arrays, as well as Bose-Hubbard [2] and Fermi-Hubbard systems [3]. I will also show how certain perturbations can enhance scarring [4] or give rise to previously unknown non-ergodic regimes [5].

[1] M. Serbyn, D. A Abanin, and Z. Papić, Nat. Phys. 17, 675 (2021).
[2] G.-X. Su, H. Sun, A. Hudomal et al., PRResearch 5, 023010 (2023).
[3] J.-Y. Desaules, A. Hudomal, C. Turner, and Z. Papić, PRL 126, 210601 (2021).
[4] A. Hudomal, J.-Y. Desaules, B. Mukherjee, G.-X. Su, J. Halimeh, and Z. Papić, PRB 106, 104302 (2022).
[5] A. Daniel, A. Hallam, J.-Y. Desaules, A. Hudomal, G.-X. Su, J. Halimeh, and Z. Papić, PRB 107, 235108 (2023).

У оквиру семинара Лабораторије за фотоакустику Института за физику у Београду, у петак, 14. новембра 2025. године у 11 часова у читаоници библиотеке „Др Драган Поповић“, др Хосе Ордоњес-Миранда (Сорбона Универзитет, CNRS, Париски институт за нанонауке (INSP), Париз, Француска) одржаће предавање:

Phonon-Polariton Thermal Waves

САЖЕТАК:

Based on the Boltzmann transport equation, we derive and analyze analytical expressions for the temperature and heat flux profiles of thermal waves propagating along nanofilms supporting the propagation of phonons and polaritons. In contrast to the typical temperature amplitude decreasing monotonically as the modulation frequency increases, we show that the amplitude of the phonon polariton temperature field exhibits a peak whose intensity and frequency of occurrence increase with the
polariton thermal conductivity of the film. This peak thus represents the fingerprints of the polariton contribution to the in-plane heat conduction, and therefore it can be used to measure the polariton thermal conductivity through photothermal and electrothermal techniques [1,2]. In particular, the developed theory together with the 3 method is applied to measure the polariton thermal conductivity of SiN nanofilms deposited on a silicon substrate. For a 50-nm-thick SiN film at 400 K, we find a polariton thermal conductivity of 0.7 Wm1K1, which represents about 50% of its phonon counterpart. This enhancement of heat conduction is well-predicted by fluctuational electrodynamics and an analytical model based on a two-dimensional gas of polaritons. The obtained results are thus expected to open a new research avenue for the polaritonic thermal characterization of nanostructures via modulated temperature fields.

[1] Y. Wu, J. Ordonez-Miranda, L. Jalabert, S. Tachikawa, R. Anufriev, H. Fujita, S. Volz, M. Nomura, Observation of heat transport mediated by the propagation distance of surface phonon-polaritons over hundreds of micrometres, Appl. Phys. Lett. 121, 112203 (2022) https://doi.org/10.1063/5.0100506
[2] Y. Wu, J. Ordonez-Miranda, S. Gluchko, R. Anufriev, D. De Sousa Meneses, L. Del Campo, S. Volz and M. Nomura, Enhanced thermal conduction by surface phonon-polaritons, Sci. Adv. 6, eabb4461 (2020) https://doi.org/10.1126/sciadv.abb4461