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Synchronization of Large Josephson-Junction Arrays by Traveling Electromagnetic Waves
Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Institute for Physics of Microstructures RAS, Russia.
Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.ORCID-id: 0000-0003-4815-5856
Vise andre og tillknytning
Rekke forfattare: 72018 (engelsk)Inngår i: Physical Review Applied, E-ISSN 2331-7019, Vol. 9, nr 5, artikkel-id 054032Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Mutual synchronization of many Josephson junctions is required for superradiant enhancement of the emission power. However, the larger the junction array is, the more difficult is the synchronization, especially when the array size becomes much larger than the emitted wavelength. Here, we study experimentally Josephson emission from such larger-than-the-wavelength Nb/NbSi/Nb junction arrays. For one of the arrays we observe a clear superradiant enhancement of emission above a threshold number of active junctions. The arrays exhibit strong geometrical resonances, seen as steps in current-voltage characteristics. However, radiation patterns of the arrays have forward-backward asymmetry, which is inconsistent with the solely geometrical resonance (standing-wave) mechanism of synchronization. We argue that the asymmetry provides evidence for an alternative mechanism of synchronization mediated by unidirectional traveling-wave propagation along the array (such as a surface plasmon). In this case, emission occurs predominantly in the direction of propagation of the traveling wave. Our conclusions are supported by numerical modeling of Josephson traveling-wave antenna. We argue that such a nonresonant mechanism of synchronization opens a possibility for phase locking of very large arrays of oscillators.

sted, utgiver, år, opplag, sider
2018. Vol. 9, nr 5, artikkel-id 054032
Emneord [en]
Josephson junction arrays, coherent THz sources, Synchronization
HSV kategori
Forskningsprogram
fysik
Identifikatorer
URN: urn:nbn:se:su:diva-157734DOI: 10.1103/PhysRevApplied.9.054032ISI: 000433041700002Scopus ID: 2-s2.0-85047735487OAI: oai:DiVA.org:su-157734DiVA, id: diva2:1236648
Tilgjengelig fra: 2018-08-03 Laget: 2018-08-03 Sist oppdatert: 2022-10-26bibliografisk kontrollert
Inngår i avhandling
1. Superradiant THz wave emission from arrays of Josephson junctions
Åpne denne publikasjonen i ny fane eller vindu >>Superradiant THz wave emission from arrays of Josephson junctions
2020 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]

High-power, continuous-wave, compact and tunable THz sources are needed for a large variety of applications. Development of power-efficient sources of electromagnetic radiation in the 0.1-10 THz range is a difficult technological problem, known as the “THz gap.” Josephson junctions allow creation of monochromatic THz sources with an inherently broad range of tunability. However, emission power from a single junction is too small. It can be amplified in a coherent superradiant manner by phase-locking of many junctions. In this case, the emission power should increase as a square of the number of phase-locked junctions.The aim of this thesis is to study a possibility of achieving coherent super-radiant emission with significant power and frequency tunability from Joseph-son junction arrays. Two types of devices are studied, based either on stacks (one-dimensional arrays) of intrinsic Josephson junctions naturally formed in single crystals of high-temperature cuprate superconductor Bi2Sr2CaCu2O8+x, or two-dimensional arrays of artificial low-temperature superconducting Nb/NbSi/Nb junctions. Micron-size junctions are fabricated using micro- and nanofabrication tools.The first chapter of this thesis describes the theory of Josephson junctions and how mutual coupling between Josephson junctions can lead to self-syn-chronization, facilitating the superradiant emission of electromagnetic radia-tion. The second chapter is focused on the technical aspects of this work, with detailed descriptions of sample fabrication and experimental techniques. The third chapter presents main results and discussion. It is demonstrated that de-vices based on high-Tc cuprates allow tunable emission in a very broad fre-quency range 1-11 THz. For low- Tc junction arrays synchronization of up to 9000 junctions is successfully achieved. It is argued that an unconventional traveling-waves mechanism facilitates the phase-locking of such huge arrays. The obtained results confirm a possibility of creation of high-power, continu-ous-wave, compact and tunable THz sources, based on arrays of Josephson junctions.

sted, utgiver, år, opplag, sider
Stockholm: Department of Physics, Stockholm University, 2020. s. 67
Emneord
Josephson junction, Superconductor, ThZ emission, high-Tc
HSV kategori
Forskningsprogram
fysik
Identifikatorer
urn:nbn:se:su:diva-181234 (URN)978-91-7911-178-6 (ISBN)978-91-7911-179-3 (ISBN)
Disputas
2020-09-09, sal FR4, AlbaNova universitetscentrum, Roslagstullsbacken 21, Stockholm, 13:00 (engelsk)
Opponent
Veileder
Tilgjengelig fra: 2020-08-17 Laget: 2020-04-28 Sist oppdatert: 2022-03-04bibliografisk kontrollert

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Borodianskyi, Evgenii A.Krasnov, Vladimir M.

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