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Król M, Septembre I, Oliwa P, Kędziora M, Łempicka-Mirek K, Muszyński M, Mazur R, Morawiak P, Piecek W, Kula P, Bardyszewski W, Lagoudakis PG, Solnyshkov DD, Malpuech G, Piętka B, Szczytko J. Annihilation of exceptional points from different Dirac valleys in a 2D photonic system. Nat Commun 2022; 13:5340. [PMID: 36096889 PMCID: PMC9468178 DOI: 10.1038/s41467-022-33001-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2022] [Accepted: 08/26/2022] [Indexed: 12/03/2022] Open
Abstract
Topological physics relies on Hamiltonian’s eigenstate singularities carrying topological charges, such as Dirac points, and – in non-Hermitian systems – exceptional points (EPs), lines or surfaces. So far, the reported non-Hermitian topological transitions were related to the creation of a pair of EPs connected by a Fermi arc out of a single Dirac point by increasing non-Hermiticity. Such EPs can annihilate by reducing non-Hermiticity. Here, we demonstrate experimentally that an increase of non-Hermiticity can lead to the annihilation of EPs issued from different Dirac points (valleys). The studied platform is a liquid crystal microcavity with voltage-controlled birefringence and TE-TM photonic spin-orbit-coupling. Non-Hermiticity is provided by polarization-dependent losses. By increasing the non-Hermiticity degree, we control the position of the EPs. After the intervalley annihilation, the system becomes free of any band singularity. Our results open the field of non-Hermitian valley-physics and illustrate connections between Hermitian topology and non-Hermitian phase transitions. The authors study a liquid crystal microcavity with polarization-dependent absorption, a source of non-Hermiticity. The transition in the Hermitian topology of the spin-orbit coupling makes possible the annihilation of exceptional points.
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Sikora B, Kowalik P, Mikulski J, Fronc K, Kamińska I, Szewczyk M, Konopka A, Zajdel K, Minikayev R, Sobczak K, Zaleszczyk W, Borodziuk A, Rybusiński J, Szczytko J, Sienkiewicz A, Wojciechowski T, Stępień P, Frontczak-Baniewicz M, Łapiński M, Wilczyński G, Paszkowicz W, Twardowski A, Elbaum D. Mammalian cell defence mechanisms against the cytotoxicity of NaYF 4:(Er,Yb,Gd) nanoparticles. Nanoscale 2017; 9:14259-14271. [PMID: 28914943 DOI: 10.1039/c7nr03705h] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Water-soluble upconversion nanoparticles (UCNPs), based on polyvinylpyrrolidone (PVP)-coated NaYF4:Er3+,Yb3+,Gd3+, with various concentrations of Gd3+ ions and relatively high upconversion efficiencies, were synthesized. The internalization and cytotoxicity of the thus obtained UCNPs were evaluated in three cell lines (HeLa, HEK293 and astrocytes). No cytotoxicity was observed even at concentrations of UCNPs up to 50 μg ml-1. The fate of the UCNPs within the cells was studied by examining their upconversion emission spectra with confocal microscopy and confirming these observations with transmission electron microscopy. It was found that the cellular uptake of the UCNPs occurred primarily by clathrin-mediated endocytosis, whereas they were secreted from the cells via lysosomal exocytosis. The results of this study, focused on the mechanisms of the cellular uptake, localization and secretion of UCNPs, demonstrate, for the first time, the co-localization of UCNPs within discrete cell organelles.
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Affiliation(s)
- B Sikora
- Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 42/46, PL-02668, Warsaw, Poland.
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Piętka B, Bobrovska N, Stephan D, Teich M, Król M, Winnerl S, Pashkin A, Mirek R, Lekenta K, Morier-Genoud F, Schneider H, Deveaud B, Helm M, Matuszewski M, Szczytko J. Doubly Dressed Bosons: Exciton Polaritons in a Strong Terahertz Field. Phys Rev Lett 2017; 119:077403. [PMID: 28949662 DOI: 10.1103/physrevlett.119.077403] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2017] [Indexed: 06/07/2023]
Abstract
We demonstrate the existence of a novel quasiparticle, an exciton in a semiconductor doubly dressed with two photons of different wavelengths: a near infrared cavity photon and terahertz (THz) photon, with the THz coupling strength approaching the ultrastrong coupling regime. This quasiparticle is composed of three different bosons, being a mixture of a matter-light quasiparticle. Our observations are confirmed by a detailed theoretical analysis, treating quantum mechanically all three bosonic fields. The doubly dressed quasiparticles retain the bosonic nature of their constituents, but their internal quantum structure strongly depends on the intensity of the applied terahertz field.
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Affiliation(s)
- B Piętka
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093 Warsaw, Poland
| | - N Bobrovska
- The Institute of Physics, Polish Academy of Sciences, al. Lotników 32/46, 02-668 Warsaw, Poland
| | - D Stephan
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093 Warsaw, Poland
- Institute of Ion Beam Physics and Materials Research, HZDR, P.O. Box 510119, 01314 Dresden, Germany
| | - M Teich
- Institute of Ion Beam Physics and Materials Research, HZDR, P.O. Box 510119, 01314 Dresden, Germany
| | - M Król
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093 Warsaw, Poland
| | - S Winnerl
- Institute of Ion Beam Physics and Materials Research, HZDR, P.O. Box 510119, 01314 Dresden, Germany
| | - A Pashkin
- Institute of Ion Beam Physics and Materials Research, HZDR, P.O. Box 510119, 01314 Dresden, Germany
| | - R Mirek
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093 Warsaw, Poland
| | - K Lekenta
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093 Warsaw, Poland
| | - F Morier-Genoud
- Institute of Physics, Ecole Polytechnique Fédérale de Lausanne (EPFL), Station 3, 1015 Lausanne, Switzerland
| | - H Schneider
- Institute of Ion Beam Physics and Materials Research, HZDR, P.O. Box 510119, 01314 Dresden, Germany
| | - B Deveaud
- Institute of Physics, Ecole Polytechnique Fédérale de Lausanne (EPFL), Station 3, 1015 Lausanne, Switzerland
- Ecole Polytechnique, F-91128 Palaiseau, France
| | - M Helm
- Institute of Ion Beam Physics and Materials Research, HZDR, P.O. Box 510119, 01314 Dresden, Germany
| | - M Matuszewski
- The Institute of Physics, Polish Academy of Sciences, al. Lotników 32/46, 02-668 Warsaw, Poland
| | - J Szczytko
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093 Warsaw, Poland
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Portella-Oberli MT, Berney J, Kappei L, Morier-Genoud F, Szczytko J, Deveaud-Plédran B. Dynamics of Trion formation in InxGa1-xAs quantum wells. Phys Rev Lett 2009; 102:096402. [PMID: 19392539 DOI: 10.1103/physrevlett.102.096402] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/24/2008] [Revised: 01/23/2009] [Indexed: 05/27/2023]
Abstract
We show a double path mechanism for the formation of charged excitons (trions); they are formed through bi- and trimolecular processes. This directly implies that both negatively and positively charged excitons coexist in a quantum well, even in the absence of excess carriers. The model is substantiated by time-resolved photoluminescence experiments performed on a very high quality InxGa1-xAs quantum well sample, in which the photoluminescence contributions at the energy of the trion and exciton and at the band edge can be clearly separated and traced over a broad range of times and densities. The unresolved discrepancy between the theoretical and experimental radiative decay time of the exciton in a doped semiconductor quantum well is explained by the same model.
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Affiliation(s)
- M T Portella-Oberli
- Institut de Photonique et Electronique Quantiques, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH1015 Lausanne, Switzerland
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Kappei L, Szczytko J, Morier-Genoud F, Deveaud B. Direct observation of the mott transition in an optically excited semiconductor quantum well. Phys Rev Lett 2005; 94:147403. [PMID: 15904111 DOI: 10.1103/physrevlett.94.147403] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2004] [Indexed: 05/02/2023]
Abstract
We have studied density-dependent time-resolved photoluminescence from a 80 A InGaAs/GaAs single quantum well excited by picosecond pulses. We succeed in giving evidence for the transition from an exciton-dominated population to an unbound electron-hole pair population as the pair density increases. For pair densities below this excitonic Mott transition we observe a spectrally separate emission from free electron-hole pairs in addition to excitonic luminescence, thereby proving the coexistence of both species. Exciton binding energy and band gap remain unchanged even near the upper bound of this coexistence region. Above the Mott density we observe a purely exponential high energy tail of the photoluminescence and a redshift of the band gap with pair density. The transition occurs gradually between 1 x 10(10) and 1 x 10(11) cm(-2) at the carrier temperatures of our experiment.
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Affiliation(s)
- L Kappei
- Ecole Polytechnique Fédérale de Lausanne, EPFL, CH-1015 Lausanne, Switzerland
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Szczytko J, Kappei L, Berney J, Morier-Genoud F, Portella-Oberli MT, Deveaud B. Determination of the exciton formation in quantum wells from time-resolved interband luminescence. Phys Rev Lett 2004; 93:137401. [PMID: 15524755 DOI: 10.1103/physrevlett.93.137401] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2003] [Indexed: 05/24/2023]
Abstract
We present the results of a detailed time-resolved luminescence study carried out on a very high quality InGaAs quantum well sample where the contributions at the energy of the exciton and at the band edge can be clearly separated. We perform this experiment with a spectral resolution and a sensitivity of the setup, allowing us to keep the observation of these two separate contributions over a broad range of times and densities. This allows us to directly evidence the exciton formation time, which depends on the density as expected from theory. We also denote the dominant contribution of excitons to the luminescence signal, and the lack of thermodynamical equilibrium at low densities.
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Affiliation(s)
- J Szczytko
- Institut de Photonique et Electronique Quantiques, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH1015 Lausanne, Switzerland
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Affiliation(s)
- J. Szczytko
- Institut de Photonique et Electronique Quantiques, Ecole Polytechnique Fédérale de Lausanne (EPFL) 1015 Lausanne, Switzerland
| | - L. Kappei
- Institut de Photonique et Electronique Quantiques, Ecole Polytechnique Fédérale de Lausanne (EPFL) 1015 Lausanne, Switzerland
| | - F. Morier‐Genoud
- Institut de Photonique et Electronique Quantiques, Ecole Polytechnique Fédérale de Lausanne (EPFL) 1015 Lausanne, Switzerland
| | - T. Guillet
- Institut de Photonique et Electronique Quantiques, Ecole Polytechnique Fédérale de Lausanne (EPFL) 1015 Lausanne, Switzerland
| | - M. T. Portella‐Oberli
- Institut de Photonique et Electronique Quantiques, Ecole Polytechnique Fédérale de Lausanne (EPFL) 1015 Lausanne, Switzerland
| | - B. Deveaud
- Institut de Photonique et Electronique Quantiques, Ecole Polytechnique Fédérale de Lausanne (EPFL) 1015 Lausanne, Switzerland
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