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Phase-Sensitive Evidence for the Sign-Reversal s± Symmetry of the Order Parameter in an Iron-Pnictide Superconductor Using Nb/Ba1−xNaxFe2As2 Josephson Junctions
Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Institute of Metal Physics of National Academy of Sciences of Ukraine, Ukraine.ORCID-id: 0000-0002-7212-434x
Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.ORCID-id: 0000-0003-4815-5856
Vise andre og tillknytning
Rekke forfattare: 52018 (engelsk)Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 120, nr 6, artikkel-id 067001Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Josephson current provides a phase-sensitive tool for probing the pairing symmetry. Here we present an experimental study of high-quality Josephson junctions between a conventional s-wave superconductor Nb and a multiband iron-pnictide Ba1−xNaxFe2As2. Junctions exhibit a large enough critical current density to preclude the d-wave symmetry of the order parameter in the pnictide. However, the IcRn product is very small ≃3μV, which is not consistent with the sign-preserving s++ symmetry either. We argue that the small IcRn value, along with its unusual temperature dependence, provides evidence for the sign-reversal s± symmetry of the order parameter in Ba1−xNaxFe2As2. We conclude that it is the phase sensitivity of our junctions that leads to an almost complete (below a subpercent) cancellation of supercurrents from sign-reversal bands in the pnictide.

sted, utgiver, år, opplag, sider
2018. Vol. 120, nr 6, artikkel-id 067001
Emneord [en]
Unconventional superconductivity, Tunneling, Josephson effect
HSV kategori
Forskningsprogram
fysik
Identifikatorer
URN: urn:nbn:se:su:diva-153780DOI: 10.1103/PhysRevLett.120.067001ISI: 000424193100011PubMedID: 29481253Scopus ID: 2-s2.0-85041822231OAI: oai:DiVA.org:su-153780DiVA, id: diva2:1191830
Tilgjengelig fra: 2018-03-20 Laget: 2018-03-20 Sist oppdatert: 2022-10-25bibliografisk 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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Kalenyuk, Aleksey A.Pagliero, AlessandroBorodianskyi, Evgenii A.Krasnov, Vladimir M.

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