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Temperature dependence of geometrical and velocity matching resonances in Bi2Sr2CaCu2O8+x intrinsic Josephson junctions
Stockholm University, Faculty of Science, Department of Physics.
Stockholm University, Faculty of Science, Department of Physics.
(English)Manuscript (preprint) (Other academic)
Abstract [en]

We study temperature dependence of geometrical (Fiske) and velocity-matching (Eck) resonances in the flux flow state of small Bi2Sr2CaCu2O8+x mesa structures. It is shown that the quality factor of resonances is high at low T, but rapidly decreases with increasing temperature already at T > 10 K. This indicates that self-heatingis strongly detrimental for operation of mesas as coherent THz oscillators and ultimately limits the emission power via suppression of the quality factor. We also study T-dependence of the resonant voltage and the speed of electromagnetic waves (Swihart velocity). Surprisingly it is observed that the Swihart velocity exhibits very weak T-dependence at low T, following T−dependence of the Josephson plasma frequency, rather than the expected linear T-dependence of the London penetration depth.

National Category
Condensed Matter Physics
Research subject
Physics
Identifiers
URN: urn:nbn:se:su:diva-62580OAI: oai:DiVA.org:su-62580DiVA: diva2:443113
Available from: 2011-09-23 Created: 2011-09-23 Last updated: 2011-09-23Bibliographically approved
In thesis
1. Properties of small Bi2Sr2CaCu2O8 intrinsic Josephson junctions: confinement, flux-flow and resonant phenomena
Open this publication in new window or tab >>Properties of small Bi2Sr2CaCu2O8 intrinsic Josephson junctions: confinement, flux-flow and resonant phenomena
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis, intrinsic Josephson junctions, naturally formed in the strongly anisotropic high-temperature superconductor Bi2Sr2CaCu2O8 (Bi-2212), are studied experimentally. For this purpose, small mesa structures are fabricated on the surface of single crystals using micro- and nano-fabrication tools, focused ion beam is used to reduce the area of the mesa-structures down to ≈ 1 × 1 μm2.

The properties of charge transport across copper-oxide layers inside the mesas are studied by intrinsic tunneling spectroscopy. Temperature, bias and magnetic field dependences of current-voltage characteristics are examined.

In the main part of the thesis, the behavior of intrinsic Josephson junctions in magnetic fields B parallel to the copper-oxide planes is studied. Parallel magnetic fields penetrate the junctions in the form of Josephson vortices (fluxons). At high magnetic fields, fluxons are arranged in a regular lattice and are accelerated by a sufficient high transport current. As the fluxon lattice is moving through the mesa, it emits electromagnetic waves in the important THz frequency range. Properties of Bi-2212 mesas in this flux-flow regime are studied in this thesis.

The following new observations were made during the course of this work: a crossover from thermal activation above Tc to quantum tunneling below Tc is seen in the interlayer transport-mechanism, the Fraunhofer pattern of Ic(B) is observed clearly in Bi-2212, superluminal electromagnetic cavity resonances and phonon-polaritons are observed in Bi-2212.

It is argued that the employed technique for miniaturization of mesas and the obtained results can be useful for a better understanding of fundamental properties of high-temperature superconductors and for the realizations of coherent flux-flow oscillators and coherent phonon-polariton generators in the important THz frequency range.

Place, publisher, year, edition, pages
Stockholm: Department of Physics, Stockholm University, 2011. 105 p.
Keyword
high-temperature superconductivity, intrinsic Josephson junctions, tunneling, fluxons, flux-flow oscillator, THz-emission, cavity resonances, polaritons, micro/nano-fabrication
National Category
Condensed Matter Physics
Research subject
Physics
Identifiers
urn:nbn:se:su:diva-62583 (URN)978-91-7447-358-2 (ISBN)
Public defence
2011-10-27, FB41, AlbaNova universitetscentrum, Roslagstullsbacken 21, Stockholm, 13:00 (English)
Opponent
Supervisors
Note
At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 6: Manuscript. Available from: 2011-10-05 Created: 2011-09-23 Last updated: 2011-10-07Bibliographically approved

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http://arxiv.org/abs/1107.5961v1

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Katterwe, Sven-OlofKrasnov, Vladimir M.
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