Abstract
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.
Original language  English 

Qualification  Doctor Degree 
Awarding Institution 

Supervisors/Advisors 

Award date  9 Nov 2004 
Place of Publication  Espoo 
Publisher  
Print ISBNs  9513864189 
Electronic ISBNs  9513864197 
Publication status  Published  2004 
MoE publication type  G5 Doctoral dissertation (article) 
Keywords
 Josephson junction
 quantum metrology
 mesoscopic tunnel junctions
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Hassel, J. (2004). Josephson junctions in charge and phase picture: Theory and applications: Dissertation. VTT Technical Research Centre of Finland. http://www.vtt.fi/inf/pdf/publications/2004/P551.pdf