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

У оквиру семинара Групе за гравитацију, честице и поља, у петак, 7. новембра 2025. године, у 11:15 у сали 360 Института за физику у Београду, др Андреј Јегоров (Институт за физику у Београду) одржаће предавање:

Dark matter phenomenon and my work on indirect dark matter searches

САЖЕТАК:

I will review the discovery history of dark matter (DM), its role in early and present Universe with implications for DM models. Then I will talk about all main contemporary DM candidates: weakly interacting massive particles (WIMPs), axions, sterile neutrinos, primordial black holes and others. WIMP paradigm will be discussed in more details. In the second part I will tell about my work on indirect WIMP searches and constraints. This comprises the search near the Galactic center in microwave band, constraints from radio observations of Andromeda galaxy (M31). Another direction employs gamma-ray band: observations of M31 again, as well as nearby supermassive black holes. Finally I will summarize the global status of WIMP indirect searches and future possibilities for DM discovery.