ORCID Profile
0000-0001-6326-4079
Current Organisations
Çankırı Karatekin University
,
Princeton University
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Publisher: American Physical Society (APS)
Date: 05-08-2019
Publisher: American Physical Society (APS)
Date: 21-12-2005
Publisher: Springer Science and Business Media LLC
Date: 09-08-2018
DOI: 10.1038/S41467-018-05349-4
Abstract: A bosonic condensate of exciton polaritons in a semiconductor microcavity is a macroscopic quantum state subject to pumping and decay. The fundamental nature of this driven-dissipative condensate is still under debate. Here, we gain an insight into spontaneous condensation by imaging long-lifetime exciton polaritons in a high-quality inorganic microcavity in a single-shot optical excitation regime, without averaging over multiple condensate realisations. We demonstrate that condensation is strongly influenced by an incoherent reservoir and that the reservoir depletion, the so-called spatial hole burning, is critical for the transition to the ground state. Condensates of photon-like polaritons exhibit strong shot-to-shot fluctuations and density filamentation due to the effective self-focusing associated with the reservoir depletion. In contrast, condensates of exciton-like polaritons display smoother spatial density distributions and are second-order coherent. Our observations show that the single-shot measurements offer a unique opportunity to study fundamental properties of non-equilibrium condensation in the presence of a reservoir.
Publisher: American Physical Society (APS)
Date: 15-07-2019
Publisher: American Physical Society (APS)
Date: 23-06-2003
Publisher: AIP Publishing
Date: 23-02-1987
DOI: 10.1063/1.98175
Abstract: The heteroepitaxial quality of (100) Si films on (11̄02) sapphire substrates (SOS) as measured by Rutherford backscattering (RBS) and x-ray pole figure analysis is improved by a rapid thermal anneal (RTA) after deposition which brings the Si temperature above 1350 °C for at least several seconds. For a 6000-Å (100) SOS film the (100) aligned to random RBS yield improves from 10% and 54% at the front and back interfaces, to as low as 3.2% and 13% after the RTA. The microtwin volume shows a corresponding decrease to under 1% from the as-grown value of 2.7%. A model based on isothermal solid phase epitaxial regrowth from the untwinned material near the front surface is proposed to account for these results.
Publisher: American Physical Society (APS)
Date: 09-02-2018
Publisher: Elsevier BV
Date: 2002
Publisher: Springer Science and Business Media LLC
Date: 19-02-2020
Publisher: AIP Publishing
Date: 19-10-1987
DOI: 10.1063/1.98697
Abstract: Scanned zone-melt recrystallization (ZMR) of amorphous Si 1-μm films on SiO2 results in subboundary-free material provided the thermal gradient along the scan is reduced to 4 K/mm or less. Below this value the usual ZMR subboundaries consisting of networks of in-plane edge dislocations are replaced by rows of threading dislocations. We account for the two kinds of crystallization by extending the faceted solidification model that we developed previously. We consider profiles of the solidification front at the intersections of {111} facet pairs where subboundaries are known to form, and postulate that the profiles are aligned approximately normal to the scan in the high gradient case, but become tilted toward the plane of the SiO2 cap layer for the low gradient case. The tilting accounts in a natural way for subboundary removal and the transition from in-plane to threading dislocations.
Publisher: Springer Science and Business Media LLC
Date: 22-01-2020
DOI: 10.1038/S41467-019-14243-6
Abstract: Superfluidity, first discovered in liquid 4 He, is closely related to Bose–Einstein condensation (BEC) phenomenon. However, even at zero temperature, a fraction of the quantum liquid is excited out of the condensate into higher momentum states via interaction-induced fluctuations—the phenomenon of quantum depletion. Quantum depletion of atomic BECs in thermal equilibrium is well understood theoretically but is difficult to measure. This measurement is even more challenging in driven-dissipative exciton–polariton condensates, since their non-equilibrium nature is predicted to suppress quantum depletion. Here, we observe quantum depletion of a high-density exciton–polariton condensate by detecting the spectral branch of elementary excitations populated by this process. Analysis of this excitation branch shows that quantum depletion of exciton–polariton condensates can closely follow or strongly deviate from the equilibrium Bogoliubov theory, depending on the exciton fraction in an exciton polariton. Our results reveal beyond mean-field effects of exciton–polariton interactions and call for a deeper understanding of the relationship between equilibrium and non-equilibrium BECs.
Publisher: Springer Science and Business Media LLC
Date: 12-07-2023
Publisher: Springer Science and Business Media LLC
Date: 28-08-2018
DOI: 10.1038/S41467-018-06064-W
Abstract: The original PDF version of this Article had an incorrect Published online date of 25 December 2018 it should have been 9 August 2018. This has been corrected in the PDF version of the Article. The HTML version was correct from the time of publication.
Publisher: American Physical Society (APS)
Date: 28-10-2021
Publisher: Springer Science and Business Media LLC
Date: 21-01-2019
DOI: 10.1007/S12640-019-9997-4
Abstract: Upregulation of the kynurenine pathway (KP) of tryptophan metabolism is commonly observed in neurodegenerative disease. When activated, L-kynurenine (KYN) increases in the periphery and central nervous system where it is further metabolised to other neuroactive metabolites including 3-hydroxykynurenine (3-HK), kynurenic acid (KYNA) and quinolinic acid (QUIN). Particularly biologically relevant metabolites are 3-HK and QUIN, formed downstream of the enzyme kynurenine 3-monooxygenase (KMO) which plays a pivotal role in maintaining KP homeostasis. Indeed, excessive production of 3-HK and QUIN has been described in neurodegenerative disease including Alzheimer's disease and Huntington's disease. In this study, we characterise KMO activity in human primary neurons and identified new mechanisms by which KMO activation mediates neurotoxicity. We show that while transient activation of the KP promotes synthesis of the essential co-enzyme nicotinamide adenine dinucleotide (NAD
Publisher: American Physical Society (APS)
Date: 29-06-2022
Publisher: Optica Publishing Group
Date: 11-08-2021
Abstract: Topological insulators are a class of electronic materials exhibiting robust edge states immune to perturbations and disorder. This concept has been successfully adapted in photonics, where topologically nontrivial waveguides and topological lasers were developed. However, the exploration of topological properties in a given photonic system is limited to a fabricated s le, without the flexibility to reconfigure the structure in situ . Here, we demonstrate an all-optical realization of the orbital Su–Schrieffer–Heeger model in a microcavity exciton-polariton system, whereby a cavity photon is hybridized with an exciton in a GaAs quantum well. We induce a zigzag potential for exciton polaritons all-optically by shaping the nonresonant laser excitation, and measure directly the eigenspectrum and topological edge states of a polariton lattice in a nonlinear regime of bosonic condensation. Furthermore, taking advantage of the tunability of the optically induced lattice, we modify the intersite tunneling to realize a topological phase transition to a trivial state. Our results open the way to study topological phase transitions on-demand in fully reconfigurable hybrid photonic systems that do not require sophisticated s le engineering.
Publisher: American Physical Society (APS)
Date: 15-02-2021
No related grants have been discovered for Loren Pfeiffer.