Josephson junctions in charge and phase picture : theory and applications

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Doctoral thesis (article-based)
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38, [40]
VTT publications, 551
Properties of weak links between two superconductors, or Josephson junctions, make them interesting for fundamental physics research. Since their discovery over four decades ago, they have provided a unique way to study the behavior of the superconducting quantum phase. More recently, ultra small, or mesoscopic, Josephson junctions with substantial single Cooper pair charging energy have gained interest due to their behavior as macroscopic quantum objects. In addition to the theoretical interest, Josephson junctions can be used as active elements in circuit applications. Particularly, in this Thesis we study two different devices. We develop the required theoretical treatments, derive device properties, and compare the results with experimental data. The first application is a Josephson voltage standard based on externally damped Superconductor - Insulator - Superconductor junctions. It consists of an array of large Josephson junctions connected in series and irradiated with a 70 GHz microwave signal. Phase locking the Josephson dynamics into the signal leads to the quantization of the voltage. This is utilized in metrology. We introduce a new circuit solution based on frequency dependent damping of the junctions. Optimization and some designs for practical arrays are presented. The purpose is to find such a design that the array is fast, has low power consumption and is as stable as possible. Arrays able to generate DC voltages of order 1 volt with metrological accuracy are demonstrated experimentally and their applicability in AC voltage calibrations is analyzed. The second application is the Bloch Oscillating Transistor (BOT). The BOT is based on controlling the Cooper pair current in an ultra small Josephson junction by means of quasiparticles tunneling through a normal junction. As part of the thesis work, the principle of operation is first demonstrated computationally. The model is then refined to yield quantitative predictions of the characteristics. Finally, an analytic theory for the device is developed and the properties as an amplifier are derived.
Josephson junctions, quantum metrology, mesoscopic tunnel junctions
Other note
  • Hassel, J., Seppä, H., Grönberg, L. and Suni, I. 2001. SIS Junctions with Frequency Dependent Damping for a Programmable Josephson Voltage Standard. IEEE Trans. Instrum. Meas. Vol. 50, No. 2, pp. 195-198. [article1.pdf] © 2001 IEEE. By permission.
  • Hassel, J., Seppä, H., Grönberg, L. and Suni, I. 2003. Optimization of a Josephson Voltage Array Based on Frequency Dependently Damped Superconductor - Insulator - Superconductor Junctions. Rev. Sci. Instrum. Vol. 74, No. 7, pp. 3510-3515. [article2.pdf] © 2003 American Institute of Physics. By permission.
  • Hassel, J., Grönberg, L., Helistö, P, Seppä, H., Nissilä, J. and Kemppinen, A. 2004. Fast Josephson Arrays for Voltage and Impedance Metrology. Conference of Precision Electromagnetic Measurements. London, 27 June - 2 July 2004, Conference Digest, pp. 154-155. [article3.pdf] © 2004 IEEE. By permission.
  • Hassel, J. and Seppä, H. 2001. Analysis of the Bloch Oscillating Transistor. IEEE Trans. Appl. Supercond. Vol. 11, No. 1, pp. 260-262. [article4.pdf] © 2001 IEEE. By permission.
  • Delahaye, J, Hassel, J., Lindell, Sillanpää R., Paalanen, M. Seppä. H. and Hakonen, P. 2003. Low-Noise Current Amplifier Based On Mesoscopic Josephson Junction. Science, Vol. 299, pp. 1045-1048. [article5.pdf] © 2003 The American Association for the Advancement of Science. By permission.
  • Hassel, J. Seppä, H., Delahaye, J. and Hakonen, P. 2004. Control of Coulomb Blockade in a Mesoscopic Josephson Junction Using Single Electron Tunneling. J. Appl. Phys. Vol. 95, No. 12, pp. 8059-8062. [article6.pdf] © 2004 American Institute of Physics. By permission.
  • Hassel, J. and Seppä. H. Theory of the Bloch Oscillating Transistor. Submitted for publication. [article7.pdf] © 2004 by authors.
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