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Seminarium Fizyki Ciała Stałego

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Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 10:15

prof. Antonio Polimeni (Dipartimento di Fisica, Sapienza Università di Roma, Italy)

Two-dimensional crystal bubbles as a platform for exploring the elastic, electronic and optical properties of two-dimensional crystals

Van der Waals (vdW) crystals have attracted great interest for the exceptional electronic, optical, chemical, and mechanical properties they reveal in their two-dimensional (2D) form. Furthermore, they are extremely flexible, so that they can sustain unprecedentedly high strains as compared to conventional low-dimensional semiconductors.In this seminar, we show how micro-scale mechanical deformations in 2D crystals represent an ideal platform to study their fundamental properties. More specifically, we exploit the capability of hydrogen-ion irradiation to induce the formation of atomically thin micro/nano-bubbles made of transition metal dichalcogenides (or TMDs, such as MoS2 or WS2) and hexagonal boron nitride. These bubbles both modify the opto-electronical properties of the crystal and represent a unique system to study the mechano-elastic and adhesive properties of vdW crystals and heterostructures. Strain is not only a consequence of the bubble mechanical deformation but we show that it prompts the opportunity to unveil subtle exciton hybridization phenomena in TMD bubbles investigated by Zeeman-splitting spectroscopy. Finally, we present the fabrication of spatially ordered arrays of bubbles operating as single photon sources.UwagaSeminarium w trybie HybrydowymFaculty of Physics room 0.06link to remote mode:https://zoom.us/j/7218838148szczegóły patrz instrukcja :instrukcja: (pdf file)AttentionThe seminar in the Hybrid modeFaculty of Physics room 0.06for details see instruction :

Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 10:15

dr Krystian Michalczewski (Vigo Photonics)

“Results & challenges of InAs/InAsSb superlattice growth technology.”

Abstract:One of the most frequently used materials for the detection of mid-wavelength infrared radiation (MWIR) and long-wavelength infrared radiation (LWIR) is mercury-cadmium-telluride (HgCdTe). Despite of many advantages of this material, hazardous materials are used in the HgCdTe production process. Moreover, EU obliged their union members to reduce certain hazardous substances in electrical and electronic equipment by RoHS (restriction of hazardous substances) directive. For that reason, III-V materials like InAsSb are designated to replace HgCdTe from the market. Nowadays, due to improvement of epitaxial techniques [especially molecular beam epitaxy (MBE)], the superlattice (SL) concept presented by Esaki and Tsu in 1970 is being again presented as a potential candidate (proved by many scientific papers) to supersede MCT. During the presentation, the latest results of T2SL technology obtained in the jointed VIGO/WAT laboratory will be presented.UwagaSeminarium w trybie HybrydowymFaculty of Physics room 0.06link to remote mode:https://zoom.us/j/7218838148szczegóły patrz instrukcja :instrukcja: (pdf file)AttentionThe seminar in the Hybrid modeFaculty of Physics room 0.06for details see instruction :

Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 10:15

prof. Anatolii Belous (V.I.Vernadskii Institute of General and Inorganic Chemistry of National Academy of Sciences of Ukraine, Kyiv)

Functional materials based on oxide systems

The report is focused on two types of functional materials: «HIGH-Q MICROWAVE DIELECTRICS» and «Ferromagnetic Nanostructures: Synthesis and Properties».In the first part of the report, there are the requirements to the parameters of MW dielectrics. It was shown that dielectrics, which have only the optical and infrared (IR) mechanisms of polarization, can possess small dielectric loses in MW range. However, IR mechanism of polarization leads to the significant temperature instability of electrophysical properties that does not satisfy the practical requirements. Different approaches are considered for the development of MW dielectrics, which would be characterized with the high values of dielectric constant, small dielectric loses and high thermal stability. Particularly, it was shown the possibility to realize the simultaneous existing the harmonic and anharmonic modes of oscillation in the structure of potassium-tungsten bronze with the complicated sub-lattices that allow significantly increasing the thermal stability of their properties. Firstly-developed multiphase systems, which high thermal stability of the properties is achieved by the effect of the volume thermal compensation. Various resonance elements for the devices of modern wireless connection (radio-filters, solid-state generators etc.) are prepared based on the developed new MW materials.The second part of the report consider the conditions of obtaining the weakly-agglomerated ferromagnetic nanoparticles with different structures. Composite resonance elements and magnetic fluids are developed based on them. The origin of the high SLP values (specific loss power) in the magnetic nanoparticles is also discussed. Examples of application of ferromagnetic nanoparticles in engineering and medicine are also demonstrated in this report.UwagaSeminarium w trybie HybrydowymFaculty of Physics room 0.06link to remote mode:https://zoom.us/j/7218838148szczegóły patrz instrukcja :instrukcja: (pdf file)AttentionThe seminar in the Hybrid modeFaculty of Physics room 0.06for details see instruction :

Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 10:15

prof. Guillaume CASSABOIS (Laboratoire Charles Coulomb UMR5221 CNRS-UM Université de Montpellier)

“Hexagonal boron nitride ”

Hexagonal boron nitride (hBN) is an ultrawide bandgap semiconductor with a large range of basic applications relying on its low dielectric constant, high thermal conductivity, and chemical inertness. The growth of high-quality crystals in 2004 has completely renewed interest in hBN. In the context of 2D materials research, hBN is used as an ideal 2D insulator, an excellent substrate for graphene and the best barrier material in van der Waals heterostructures. hBN is also emerging as an exciting material in its own right, offering novel material properties that enable a broad range of optical, electro-optical and quantum optics functionalities in various spectral domains. It is a natural hyperbolic material in the mid-infrared range, it hosts defects that can be engineered to obtain room-temperature, single-photon emission in the ultraviolet, visible and near-infrared ranges, and it exhibits exceptional performances in the deep-ultraviolet for a new generation of emitters and detectors in the UV-C.In this talk, I will review the original properties of hBN in relation with its lamellar structure, with some illustrations in fundamental studies and applications.UwagaSeminarium w trybie HybrydowymFaculty of Physics room 0.06link to remote mode:https://zoom.us/j/7218838148szczegóły patrz instrukcja :instrukcja: (pdf file)AttentionThe seminar in the Hybrid modeFaculty of Physics room 0.06for details see instruction :

Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 10:15

dr Daniel Wigger (Politechnika Wrocławska)

Coherent control of hBN color centers: Noise characterization and phonon dynamics

For the development of scalable quantum technologies, reliable single-photon emitters in solid state systems are required. In this context, promising candidates are the recently discovered color centers in the Van der Waals insulator hBN. These color centers are attracting increasing attention due to their quantum performance at room temperatures and wide range of transition energies. In this seminar talk I will report on our recent results on the ultrafast optical coherent state manipulation of a single hBN color center [1]. By combining experiment and theory we achieve a sound understanding of the basic impact of environment noise and the coupling to phonons on the coherence properties of the emitter.[1] J. Preuss, D. Groll et al., accepted in Optica (2022)UwagaSeminarium w trybie HybrydowymFaculty of Physics room 0.06link to remote mode:https://zoom.us/j/7218838148szczegóły patrz instrukcja :instrukcja: (pdf file)AttentionThe seminar in the Hybrid modeFaculty of Physics room 0.06for details see instruction :

Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 10:15

mgr Adam Wincukiewicz (Faculty of Physics, University of Warsaw)

“Novel multidimensional perovskites for high-stability solar cells”

In the last few years, hybrid (organic-inorganic) perovskite solar cells (PSCs) have undergone exceptionally rapid advancements in power conversion efficiencies, quickly reaching the values, which took silicon solar cells decades of development. Moreover, the great potential of perovskites for applications in other optoelectronic devices, such as photodetectors, lasers and light-emitting diodes, or microcavity structures operating in the regime of strong light-matter interaction, has recently been demonstrated. High efficiencies and superior performance of perovskite-based devices is due to their high absorption coefficient, relatively low exciton binding energies, and long diffusion length and lifetime of carriers[1]. However, despite all these advantages and the resulting huge interest in perovskite structures, several serious challenges concerning the environmental stability of such devices remain to be addressed for their commercial applications and cost-competitive deployment at a large scale. In particular, it is well established that the exposure of perovskite films to moisture and oxygen leads to material degradation within days[2][3].In this work, we analyzed the degradation dynamics under different environmental conditions for so called multidimensional perovskite films (i.e., materials comprised of 2D and 3D perovskites – 2D/3D PVSK) and compared it with reference 3D perovskite samples. As expected, the study showed that our novel modification resulted in a significantly higher stability, with the characteristic degradation times for 2D/3D PVSK samples to be 5 times longer than those measured for reference 3D PVSK films. Moreover, we observed reversible and irreversible water intercalation effects (hydration and dehydration processes) in perovskite films kept under changing relative humidity. The effects of a partial iodine substitution with bromine in perovskite structure was also investigated. It was found that such a modification suppresses the hydration processes altogether, which is an extremely valuable observation from the point of view of achieving water-resistant perovskite films.[1] S.D. Stranks, et al., Phys. Rev. Appl. 2 (2014) 034007.[2] T. Leijtens, et al., Nat. Commun. 2013 41. 4 (2013) 1–8[3] A. Wincukiewicz, et al., Sol. Energy Mater. Sol. Cells. 230 (2021) 111142.UwagaSeminarium w trybie HybrydowymFaculty of Physics room 0.06link to remote mode:https://zoom.us/j/7218838148szczegóły patrz instrukcja :instrukcja: (pdf file)AttentionThe seminar in the Hybrid modeFaculty of Physics room 0.06for details see instruction :

Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 10:15

dr Katarzyna Gas (Instytut Fizyki PAN)

“Magnetic anisotropy of Mn 3+ in GaN: from paramagnetic GaN:Mn to ferromagnetic dilute (Ga,Mn)N”

GaN enriched with Mn constitutes worthwhile material system whose magnetic characteristics are set by the d-level occupancy of the Mn ions. Basing on the results of a wide temperature range magnetometry (down to 0.5 K) obtained for very high quality GaN:Mn crystals (grown by HVPE method) we will re-visit the crystal field model and show that aided by EPR results, an accurate spin counting of d5 and d4 levels is possible – constituting an indispensable characterization tool for these commercially important crystals. Next we will proceed to much concentrated epitaxial (Ga,Mn)N layers with Mn contents approaching 10%. Here, superexchange-mediated ferromagnetism develops at the low end of cryogenic temperatures. The magnetic anisotropy of such systems will be discussed and some possible means of its control will be presented.UwagaSeminarium w trybie HybrydowymFaculty of Physics room 0.06patrz instrukcja :instrukcja: (pdf file)AttentionThe seminar in the Hybrid modeFaculty of Physics room 0.06see instruction :instruction: (pdf file)

Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 10:15

prof. dr hab. inż. Michał Boćkowski (Institute of High Pressure Physics Polish Academy of Sciences)

“GaN-on-GaN technology”

Three main growth methods for crystallizing bulk GaN: i/ halide vapor phase epitaxy (HVPE); ii/ ammonothermal (basic and acidic); iii/ sodium flux will be discussed. All these methods seem to be very perspective for obtaining bulk GaN and fabricating high quality GaN substrates. Ammonothermal GaN crystals demonstrate perfect structural quality; it can still be improved and transferred to HVPE-GaN. HVPE technology is also the best for growing drift layers for electronic devices. Ultra-high-pressure annealing (UHPA) is a very promising technology for fabricating devices with selectively implanted areas.UwagaSeminarium w trybie HybrydowymFaculty of Physics room 0.06link to remote mode:https://zoom.us/j/7218838148szczegóły patrz instrukcja :instrukcja: (pdf file)AttentionThe seminar in the Hybrid modeFaculty of Physics room 0.06for details see instruction :instruction: (pdf file)

Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 10:15

prof. dr hab. T. Czyszanowski (Instytut Fizyki Politechniki Łódzkiej)

“Emitted power enhancement of laser by breaking the circular symmetry of the optical aperture ”

Emitted power enhancement of laser by breaking the circular symmetry of the optical apertureA. Brejnak, M. Gębski, M. Marciniak, M. Wasiak, J. Muszalski,J. A. Lott, I. Fischer, T. CzyszanowskiBreaking the circular symmetry of standard semiconductor vertical-cavity surface-emitting lasers’ apertures can boost their output power by more than 60% and raise their quantum efficiency by more than 10%. We explain these enhancements for certain deformations of laser circular apertures by a more uniform light intensity profile within the optical aperture due to emergence of wave chaos and a more uniform spectral distribution of the density of optical states (modes).By this work we show that the efficiency of stimulated emission can be enhanced by engineering the spectral structure of the optical resonators in general. Similar approach is used already to enhance spontaneous emission of light-emitting diodes, but has been left unexplored in the context of the stimulated emission of lasers.UwagaSeminarium w trybie HybrydowymFaculty of Physics room 0.06link to remote mode: https://zoom.us/j/7218838148szczegóły patrz instrukcja :instrukcja: (pdf file)AttentionThe seminar in the Hybrid modeFaculty of Physics room 0.06for details see instruction :instruction: (pdf file)

Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 10:15

Ph.D. D.Sc. Robert W. Góra (Faculty of Chemistry, Wroclaw University of Science and Technology, Wroclaw,)

Photochemical origins of life

The question of the origins of life ignited imagination of the mankind since the dawn of its existence. It would be difficult to outline all the scientific hypotheses that were proposed regarding the abiotic synthetic routes that led to the formation of the first single-cellular organisms about 3.8 Gy ago. However, recently there is growing evidence that all the building blocks of a protocell could form in a very similar system chemistries. The scenario proposed by Sutherland and Szostak [1, 2] involves streams flowing down the slopes of an impact crater, leaching metals and prebiotic feedstock molecules like cyanides under intense ultraviolet radiation. The latter seems to be crucial and leads to interesting photochemical transformations, necessary to produce nucleotides, aminoacids, simple sugars and lipids – all that is required to form a protocell. In this contribution an overview of the selected key steps of these reactions, as elucidated by ab initio quantum chemical calculations [3, 4, 5], shall be discussed.References1. J.D. Sutherland, Nature Reviews Chemistry, 1, 0012 (2017)2. J.W. Szostak, Molecular Frontiers Journal, 1, 1 (2017)3. J. Xu, V. Chmela, N.J. Green, D.A. Russell, M.J. Janicki, R.W. Góra, R. Szabla, A.D. Bond, J.D. Sutherland, Nature, 582, 60 (2020)4. M.J. Janicki, S.J. Roberts, J. Šponer, M.W. Powner, R.W. Góra, R. Szabla, Chem. Commun., 54, 13407 (2018)5. J. Xu, M. Tsanakopoulou, C.J. Magnani, R. Szabla, J.E. Šponer, J. Šponer, R.W. Góra, J.D. Sutherland, Nat. Chem., 9, 303 (2017)UwagaSeminarium w trybie HybrydowymFaculty of Physics room 0.06link to remote mode: https://zoom.us/j/7218838148szczegóły patrz instrukcja :instrukcja: (pdf file)AttentionThe seminar in the Hybrid modeFaculty of Physics room 0.06for details see instruction :instruction: (pdf file)

Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 10:15

dr Dariusz Sztenkiel (Institute of Physics, Polish Academy of Sciences)

“Ferromagnetic coupling in GaN doped with Mn”

Abstract(pdf file)UwagaSeminarium w trybie HybrydowymFaculty of Physics room 0.06patrz instrukcja :instrukcja: (pdf file)AttentionThe seminar in the Hybrid modeFaculty of Physics room 0.06see instruction :instruction: (pdf file)

Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 10:15

dr Mateusz Goryca (Faculty of Physics, University of Warsaw)

How to study magnetic monopoles?

In particle physics, a magnetic monopole remains a hypothetical elementary particle that has never been observed. However, certain condensed matter systems can contain effective magnetic monopoles. One of such systems are Artificial Spin Ices (ASIs) - arrays of interacting nanomagnets that have allowed the design of geometrically frustrated exotic collective states not found in natural magnets. A key emergent description of fundamental excitations in ASIs is that of mobile quasiparticles that carry an effective magnetic charge - that is magnetic monopoles. These charge excitations can interact with each other and with applied magnetic fields via the magnetic analog of the electronic Coulomb interaction, representing the emergence of a range of novel phenomena, including the possibility of "magnetricity". While the presence of monopoles in ASI has been observed in pioneering imaging measurements, dynamical studies of monopole kinetics, and (especially) the ability to tune continuously through monopole-rich regimes in thermal equilibrium, remain at an early stage.In the seminar I will present a high-bandwidth magneto-optical noise spectrometer that we have developed to passively "listen" to spontaneous magnetization fluctuations in archetypal, thermally active square ASI. The noise reveals specific regions in the magnetic field-dependent phase diagram where the density of mobile monopoles increases well over an order of magnitude compared with neighboring regimes. Moreover, detailed noise spectra demonstrate that monopole kinetics are minimally correlated (i.e., most diffusive) in this plasma-like regime. Experiments and Monte-Carlo simulations of more complex ASIs (including quadrupolar and vertex-frustrated Shakti and Tetris lattices) show similarly fascinating behavior, revealing surprisingly rich field-dependent phase diagrams of these systems.The discovery of on-demand monopole regimes with tunable kinetic properties opens the door to new probes of magnetic charge dynamics and provides a new paradigm for the studies of magnetricity in artificial magnetic materials.UwagaSeminarium w trybie HybrydowymFaculty of Physics room 0.06patrz instrukcja :instrukcja: (pdf file)AttentionThe seminar in the Hybrid modeFaculty of Physics room 0.06see instruction :instruction: (pdf file)

Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 10:15

prof. Bernard Gil (Centre National de la Recherche Scientifique Laboratoire Charles Coulomb, Montpellier)

“A journey among the optical properties of sp2-bonded boron nitride”

Boron Nitride powder, white graphite has long been an important material for an eclectic range of industrial applications some of them linked to its layered structure, its good thermal conductivity, its high melting temperature, or the huge cross section for neutron absorption of its 10B isotope, or even in the industry of cosmetics, there in straightforward relation with its exceptional brightness. Solid state physicists were not really interested about it except some theorists among which were researchers of the group of Franco Bassani at Pisa. Wolfgang Choyke had carefully measured resonances of the dielectric constant above 6 eV, but he never published his experimental results. They were, but later, used by C. Doni and G. Pastori Paravicini for consolidating their calculation of the band structure made within the context of a tight binding description(Il Nuovo Cimento B, 64, 117, 1969).BN was exhumated from its “lethargy” in 2004 when T. Taniguchi grew high structural quality bulk BN flakes with micrometric dimensions, on which K. Watanabe demonstrated lasing operation at 215 nm ( Nat. Mat., 3,404, 2004), which boosted the interest of BN into the arena of devices for ultraviolet emission.The birth of Van der Waals structure has simultaneously offered to BN a large range of complementary applications as a passive, capping material.During this seminar I will review the linear and nonlinear optical properties of the different polytypes of sp²-bonded layered BN bulk crystals and epilayers (all having indirect fundamental bandgap). I will discuss the nature and the value of the bandgap of the monolayer and I will conclude with some of the last results concerning their applications for sources of single photon emission.UwagaSeminarium w trybie HybrydowymFaculty of Physics room 0.06patrz instrukcja :instrukcja: (pdf file)AttentionThe seminar in the REMOTE modesee instruction :instruction: (pdf file)

Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 10:15

prof. dr hab. Sebastian Mackowski (Nanophotonics Group, Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, Toruń,)

“Silver nanowire – plasmonic magic wand"

The presentation will focus on advocating for uniqueness of silver nanowires, metallic structures with diameters of 100 nm and lengths up to a millimeter [1]. While the diameter of the nanowires is small enough to facilitate localized surface plasmon resonance, their length is sufficiently large to exploit propagation of energy over considerable distances. In combination with advanced nanostructural manipulation, these properties open virtually unlimited playground for interdisciplinary research, which spans over fluorescence enhancement [2-4], remote and high efficiency sensing [5-7], long-range energy propagation [8-10], controlled photocatalysis, heat propagation, etc.As all of the experiments involve some form of fluorescence microscopy and spectroscopy, surface functionalization, microdroplet deposition, and alike, essentials of the technical aspects will be discussed to the necessary detail.Experimental demonstrations will include:1. Plasmonic enhancement of protein fluorescence2. Real-time single protein detection3. Remote activation of luminescence4. Interfacing nanowires with quantum dots5. Remote photocatalysisResearch was partially financed by the National Science Centre (Poland) within the grants 2013/10/E/ST3/00034, 2013/09/D/ST3/03746, 2016/21/B/ST3/02276, 2016/22/E/ST5/00531, 2017/27/B/ST3/02457, and 2017/26/E/ST3/00209, and 2018/31/G/ST3/03596, as well as by the National Centre for Research and Development within the DZP/POLTUR-1/50/2016.References:[1] J. Niedziółka-Jönsson, S. Maćkowski, Materials 12, 1418 (2019)[2] M. Olejnik, et al. Applied Physics Letters 102, 083703 (2013)[3] M. Szalkowski, et al. Nanoscale 9, 10475 (2017)[4] M. Ćwik , et al. Opt. Express 29, 8834 (2021)[5] M. Szalkowski, et al. Sensors 18, 290 (201[6] K. Sulowska, et al. Methods Appl. Fluoresc. 8, 045004 (2020)[7] J. Grzelak, et al. Sens. Actuator B-Chem. 273, 689 (201[8] A. Prymaczek, et al. Nanoscale 10, 12841 (201[9] D. Buczyńska, et al. J. Phys. Chem. C 124,15418 (2020)[10] A. Prymaczek, et al. Sci. Rep. 11, 3557 (2021)Abstract(pdf file)UwagaSeminarium w trybie Hybrydowym
Faculty of Physics room 0.06patrz instrukcja :instrukcja: (pdf file)AttentionThe seminar in the REMOTE modesee instruction :instruction: (pdf file)

Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 10:15

prof. dr hab. Krzysztof Korona (Wydział Fizyki Uniwersytet Warszawski)

“Organic solar cells investigated by crystalline-semiconductor scientist”

From a few years, our group has been constructing and investigating solar cells based on bulk heterojunctions (BHJ). The BHJs are formed in the scale of nanometers as mixture of two compounds called donor and acceptor materials. Illumination causes excitation of electrons and holes. Due to difference in quantum levels between the two compounds, electrons go to the acceptor material and holes go to the donor material. Then the charge carriers are collected by electrodes supplying electric current and power.In the seminar I will explain how the BHJ works and present few interesting facts that we had found during our research. The organic solar cells are usually described in language used in organic chemistry. I plan to use terms more familiar to physicists working with classical, crystalline semiconductors, for example, "acceptor material" can be understood as n-type semiconductor.UwagaSeminarium w trybie HybrydowymFaculty of Physics room 0.06patrz instrukcja :instrukcja: (pdf file)AttentionThe seminar in the REMOTE modesee instruction :instruction: (pdf file)

Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 10:15

prof. dr hab. Michał Leszczyński (Instytut Wysokich Ciśnień PAN)

GaNification overview by material scientist

The talk will consist of three parts:i) GaNification in Far East. In this part, I will show a big progress inUVC emitters used for disinfection and sterilization.ii) GaNification in Unipress. In this part, I will show the recentprogress of nitride technology in our institute: bulk GaN substrategrowth, MBE and MOVPE epitaxy, laser diode technology, vertical transistortechnology.iii) GaNification in Laboratory of Semiconductor Characterization. In this part, I will show the research which should lead to 3D projectors, and howatoms diffuse in InGaN/GaN epitaxial structures.UwagaSeminarium w trybie HybrydowymFaculty of Physics room 0.06patrz instrukcja :instrukcja: (pdf file)AttentionThe seminar in the REMOTE modesee instruction :instruction: (pdf file)

Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 10:15

dr. Valérian Giesz (Cofounder of Quandela, France)

“Quandela, from the academic research in semiconductor Quantum Dots to the optical Quantum Computing”

In a first part, Dr. Valérian Giesz, CEO cofounder of Quandela, will present the principles of efficient solid-state single photon sources based on semiconductor Quantum Dots, a technology at the origin of the foundation of the company Quandela. In the second part, he will describe how these single-photon sources are used for the development of optical quantum computers.UwagaSeminarium w trybie ZDALNYMpatrz instrukcja :instrukcja: (pdf file)AttentionThe seminar in the REMOTE modesee instruction :instruction: (pdf file)

Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 10:15

dr Helgi Sigurdsson (School of Physics and Astronomy, University of Southampton, Southampton, UK Science Institute, University of Iceland, Reykjavik, Iceland)

Networks of liquid light

In this talk, I will present results on all-optically engineered macroscopic networks of connected exciton-polariton condensates, which permit studies on fundamental emergent behaviours in complex nonequilibrium dynamical systems while subject to a drive and bosonic final-state stimulation. I will explain how a uniquely polaritonic feature gives rise to so-called “ballistic condensates” which, when spatially coupled, form a bosonic condensed matter analog of time-delay coupled oscillators that are ubiquitous in nature. I will present experimental and theoretical results on large-scale condensate networks displaying aforementioned emergent behaviors, including: spontaneous synchronization with unprecedented long-range spatial and temporal correlations, strong polarization buildup and control, geometric frustration and formation of persistent superfluid currents, non-invasive optical control of the network coupling weights, and synthesis of artificial lattices with non-Hermitian flatband and topological properties.Lastly, I will discuss recent developments on the role of polariton condensate networks as nonlinear information processing elements in the optical computing paradigm.Fool abstract(pdf file) UwagaSeminarium w trybie hybrydowympatrz instrukcja :instrukcja: (pdf file)AttentionThe seminar in the hybrid modesee instruction :instruction: (pdf file)

Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 10:15

dr hab. Piotr Wojnar, prof. IF PAN (Institute of Physics Polish Academy of Sciences)

“Electron-hole separation in type II nanoscale heterostructures built of II-VI semiconductors”

The staggered band alignment characteristic for a type II semiconductor heterostructure leads to a spatial separation of conduction band electrons and valence band holes at the interface. The first part of the seminar will be devoted to our recent development of ZnTe/CdSe core/shell nanowires, in which the spatially indirect optical transition appears in the near infrared spectral range [1]. In the second part it will be demonstrated how the electron-hole spatial separation affects the emission from individual (Cd,Se)Te quantum dots embedded in ZnTe matrix [2].[1] P. Wojnar et al. Nanotechnology 32, 495202 (2021)[2] P. Baranowski et al. Applied Physics Letters 117, 113101, (2020)UwagaSeminarium w trybie hybrydowympatrz instrukcja :instrukcja: (pdf file)AttentionThe seminar in the hybrid modesee instruction :instruction: (pdf file)

Zapraszamy na spotkanie o godzinie 10:15

prof. dr hab. Michał Matuszewski (Division of Theoretical Physics Institute of Physics, Polish Academy of Sciences)

"Efficient optical computing with exciton-polaritons"

Recent years have witnessed remarkable developments in big data, artificial intelligence and neural networks. Machine learning has found wide applications in both research and the industry. This comes at the cost of high levels of energy consumption that are necessary to process large amounts of data. It is expected that over 20% of global electricity use by 2030 will be used for information processing. The performance of complementary metal-oxide semiconductors (CMOS) no longer follows Moore's law [1]. In result, much research has been aimed at finding an alternative platform for information processing, characterized by high performance and energy efficiency.In this talk I will review recent progress in machine learning with photons [2,3]. Photonic information processing benefits from high speed, parallelization, low communication losses, and high bandwidth. Fully functional photonic neurons, including spiking neurons, as well as neural networks, have been already realized in laboratories. Several networks achieved high performance in challenging machine learning tasks, such as image and video recognition.We recently demonstrated hardware neural network systems where strong optical nonlinearity results solely from interactions of exciton-polaritons, quantum superpositions of light and matter [4,5,6]. Such superpositions, in the form of mixed quasiparticles of photons and excitons, are characterized by excellent photon-mediated transport properties and strong exciton-mediated interactions. These semiconductor microcavity systems can be used to construct fully all-optical neural networks characterized by extremely high energy efficiency [7]. We show why using polaritonics in place of standard nonlinear optical phenomena, is the key to achieving such a performance.[1] M. M. Waldrop, Nature News 530, 144 (2016)[2] G. Wetzstein, A. Ozcan, S. Gigan, S. Fan, D. Englund, M. Soljacic, C. Denz, D. A. Miller, and D. Psaltis, Nature 588 , 39 (2020)[3] B. J. Shastri, A. N. Tait, T. F. de Lima, W. H. Pernice, H. Bhaskaran, C. D. Wright, and P. R. Prucnal, Nature Photonics 15, 102 (2021)[4] A. Opala, S. Ghosh, T. C. Liew, and M. Matuszewski, Physical Review Applied 11 , 064029 (2019)[5] D. Ballarini, A. Gianfrate, R. Panico, A. Opala, S. Ghosh, L. Dominici, V. Ardizzone, M. De Giorgi, G. Lerario, G. Gigli, Timothy C. H. Liew, Michal Matuszewski, and Daniele Sanvitto, Nano Letters 20, 3506 (2020)[6] R. Mirek, A. Opala, P. Comaron, M. Furman, M. Król, K. Tyszka, B. Seredynski, D. Ballarini, D. Sanvitto, Timothy C. H. Liew, Wojciech Pacuski, Jan Suffczyński, Jacek Szczytko, Michał Matuszewski, and Barbara Piętka, Nano Letters (2021)[7] M. Matuszewski, A. Opala, R. Mirek, M. Furman, M. Król, K. Tyszka, T.C.H. Liew, D. Ballarini, D. Sanvitto, J. Szczytko, B. Piętka, arXiv:2108.12648.UwagaSeminarium w trybie hybrydowympatrz instrukcja :instrukcja: (pdf file)AttentionThe seminar in the hybrid modesee instruction :instruction: (pdf file)

Zapraszamy na spotkanie o godzinie 10:15

dr V.S. Bhat (International Research Centre MagTop, Institute of Physics, Polish Academy of Sciences)

"Direct Observation of Magnon Modes in Kagome Artificial Spin Ice with Topological Defects"

Kagome artificial spin ice (KASI) is a network of Ising type nanobars on a kagome lattice. We investigate spin dynamics of a KASI consisting of Ni81Fe19 nanomagnets arranged on an interconnected kagome lattice using broadband ferromagnetic resonance (FMR), magnetic force microscopy (MFM), micro-focus Brillouin light scattering (BLS) microscopy and X-ray photoemission electron microscopy (XPEEM). Micro-focus BLS performed on magnetically disordered states exhibit a series of magnon resonances which depend on topological defect configurations. We experimentally reconfigure microstates in ASI using a 2D vector field protocol and apply microwave-assisted switching to intentionally trigger reversal. Our work is key for the creation of avalanches inside the kagome ASI and reprogrammable magnonics based on ASIs.Acknowledgement: The research was supported by the Swiss National Science Foundation via Grant No. 163016. V.S. Bhat acknowledges support from the foundation for Polish Science through the IRA Programme financed by EU within SG OP Programme.UwagaSeminarium w trybie zdalnym.patrz instrukcja :instrukcja: (pdf file)AttentionThe seminar in the remote modesee instruction :instruction: (pdf file)link do sesji Zoom/link to Zoom session:https://zoom.us/j/7218838148

Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 10:15

dr inż. Anna Musiał (Faculty of Fundamental Problems of Technology, Wroclaw University of Science and Technology)

"Quantum dot-based single-photon sources operating at telecom wavelengths"

Single-photon sources are one of the building blocks of ultra-secure quantum communication networks. A key requirement for their applicability is operation at telecom wavelengths. Epitaxial quantum dots in photonic structures surpass other approaches in terms of single-photon purity and offer compatibility with semiconductor technology what makes them a very promising platform. Properties of the state-of-the-art quantum dot-based single-photon sources will be addressed followed by a summary of recent developments and future prospects.UwagaSeminarium w trybie hybrydowympatrz instrukcja :instrukcja: (pdf file)AttentionThe seminar in the hybrid modesee instruction :instruction: (pdf file)

Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 10:15

dr Tomasz Smoleński (Quantum Photonics Group, Institute for Quantum Electronics, ETH Zürich)

"Spectroscopy of strongly correlated electrons in atomically-thin materials"

When the Coulomb repulsion between itinerant electrons dominates over their kinetic energy, the electrons in solid state materials start to develop strong correlations. A paradigm state of matter that is expected to emerge in this regime is an electronic Wigner crystal, in which the electrons spontaneously break continuous translation symmetry and arrange themselves into a periodic lattice mimicking that of the real crystals. In this talk, I will review our recent experimental explorations of strongly correlated electronic phases in transition metal dichalcogenides (TMD) and their van der Waals heterostructures. In particular, I will present our novel spectroscopic technique allowing to detect the Wigner crystal in a TMD monolayer through the periodic potential it generates for the excitons [1]. This potential allows the excitons to undergo a Bragg diffraction, which gives rise to a new, Bragg-umklapp transition in the optical excitation spectrum that heralds the presence of a crystalline electronic order. In the second part of the talk, I will also show how the TMD monolayer can be exploited as a quantum proximity sensor to optically probe the formation of fractional quantum Hall states in a nearby graphene layer [2].[1] T. Smoleński, P. E. Dolgirev, C. Kuhlenkamp, A. Popert, Y. Shimazaki, P. Back, X. Lu, M. Kroner, K. Watanabe, T. Taniguchi, I. Esterlis, E. Demler, and A. Imamoğlu, Signatures of Wigner crystal of electrons in a monolayer semiconductor. Nature 595, 53-57 (2021).[2] A. Popert, Y. Shimazaki, M. Kroner, K. Watanabe, T. Taniguchi, A. Imamoğlu, and T. Smoleński, Optical probing of fractional quantum Hall effect in graphene. to be published (2021).UwagaSeminarium w trybie hybrydowympatrz instrukcja :instrukcja: (pdf file)AttentionThe seminar in the hybrid modesee instruction :instruction: (pdf file)

Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 10:15

dr inż. Agnieszka Pieniążek (Faculty of Fundamental Problems of Technology, Wroclaw University of Science and Technology)

Hydrotermalne mikrosłupki ZnO jako rezonatory modów galerii szeptów i baza dla osiowych heterostruktur kwantowych

Hydrothermal ZnO microrods as whispering gallery mode resonators and base for axial quantum heterostructures"

Właściwości optyczne pojedynczych mikrosłupków ZnO syntetyzowanych metodą hydrotermalną wspomaganą mikrofalowo zostały zbadane za pomocą przestrzennie i spektralnie rozdzielczej spektroskopii katodoluminescencyjnej. Na seminarium przedstawię wyniki analizy stanów domieszkowych i defektowych ZnO pokazujące, że mikrosłupki syntetyzowane w optymalnych warunkach wzrostu i wygrzewania charakteryzowały się niską koncentracją rodzimych defektów punktowych i intensywną emisją ekscytonową.Mikrosłupki ZnO otrzymane w optymalnych warunkach wzrostu wykazywały przestrzenną lokalizację luminescencji przykrawędziowej przy ściankach bocznych, zwłaszcza w rogach wurcytowego sześciokąta. Niejednorodny rozkład przestrzenny luminescencji przykrawędzioweji struktura subtelna pasma przykrawędziowego zostały przeanalizowane z wykorzystaniem modelu fal płaskich pod kątem obecności modów galerii szeptów. Zjawisko rezonansu optycznego i wzmocnienie optyczne poprzecznych modów rezonansowych zostało potwierdzone przy wykorzystaniu spektroskopii katodoluminescencyjnej. Ze wzrostem mocy wzbudzania zaobserwowano zmiany w kształciei szerokości połówkowej pasma przykrawędziowego, co zostało zinterpretowane jako przejście gazu ekscytonowego w plazmę elektronowo-dziurową.Zaprezentuję także oryginalną dwuetapową metodę wzrostu umożliwiającą wyhodowanie zaawansowanych heterostruktur kwantowych ZnO/Zn1-xMgxO na powierzchni c hydrotermalnych mikrosłupków ZnO. Przestrzennie rozdzielcze pomiary katodoluminescencji potwierdziły udane wzrosty osiowych heterostruktur kwantowych zawierających pojedyncze i wielokrotne studnie kwantowe na górnej powierzchni mikrosłupków.UwagaSeminarium w trybie hybrydowympatrz instrukcja :instrukcja: (pdf file)

Optical properties of the individual ZnO microrods grown by a microwave-assisted hydrothermal method have been investigated by spatially and spectrally resolved cathodoluminescence spectroscopy and imaging. Here, the study of impurities and defects of ZnO will be presented. It reveals that optimization of the growth and annealing conditions results in ZnO microrods with low concentration of intrinsic point defects and strong excitonic emission.For ZnO microrods grown in the optimized conditions strong localization of cathodoluminescence at the six corners of the individual microrod has been revealed. Locally distributed luminescence and fine structure of near-band-edge emission was analyzed as a manifestation of whispering gallery modes of the hexagonal resonator. The optical resonance phenomena have been confirmed. Changes in the ZnO microrod emission were observed as a function of the excitation power, which can be associated with the transition from the exciton gas to electron-hole plasma conditions.I will highlight successful fabrication and optical properties of an axial Zn1−xMgxO/ZnO/Zn1-xMgxO quantum well deposited on the top of the hydrothermal ZnO microrods by molecular beam epitaxy. Comprehensive cathodoluminescence studies of local optical properties of the individual Zn1−xMgxO/ZnO/Zn1−xMgxO axial microrod structures containing single and multiple quantum wells have confirmed the growth of the axial heterostructure on the c-plane of the microrods. AttentionThe seminar in the hybrid modesee instruction :instruction: (pdf file)

Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 10:15

prof. dr hab. Adam Proń (Wydział Chemiczny Politechniki Warszawskiej)

"Synthesis and surface functionalization of binary, ternary and quaternary semiconductor nanocrystals in view of spiritual brotherhood of physicists and chemists."

After explaining these chemical notions which are vital for understanding the presented lecture, the lecturer will focus of these aspects of nanomaterials chemistry with which each decent solid state physicist should get acquainted. In particular:i) he will discuss basic synthetic procedures leading to ternary and quaternary nanocrystals via one-component or multi-component precursors;ii) he will descibe methods of organic ligands identification, presenting, in addition, all hoaxes which make the life of a naive scientist difficult;iii) he will outline methods of primary ligands exchange for functional ones, putting emphasis on their severe limitations;iv) he will recapitulate problems of post-preparative functionalization in view of the fabrication of inorganic-organic hybrides for specific applications;He will try to use simple language since he does not want to frighten physicists by using terms which are not comprehensible for them, in other words he will play a role of a humble chemist.UwagaSeminarium w trybie hybrydowympatrz instrukcja :instrukcja: (pdf file)AttentionThe seminar in the hybrid modesee instruction :instruction: (pdf file)