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I. The phase-current relation at zero voltage in proximity effect bridges. II. The interaction of proximity effect bridges with superconducting microstrip resonators

Citation

Ganz, Tomas (1976) I. The phase-current relation at zero voltage in proximity effect bridges. II. The interaction of proximity effect bridges with superconducting microstrip resonators. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechTHESIS:12062011-081306612

Abstract

Experimental investigations on the proximity effect bridge (a Josephson device) at zero voltage and at finite voltages in the µV range are reported.

The phase-super current relation at zero voltage was measured using an asymmetric superconducting quantum interferormeter circuit. The data are in agreement with the Josephson supercurrent-phase relation I_S=I_C sinδ with deviation less than 5% of the critical current I_c. The supercurrent density in the measured bridges reached as high as 50-100 µA/µm^2.

Using microcircuitry techniques, proximity effect bridges were strongly coupled to superconducting microstrip resonators. Selfinduced steps in the I-V characteristics of bridges coupled to resonators were observed in the GHz region at voltages (frequencies) corresponding to the expected modes of the resonators. Two types of steps were seen depending on whether the resonator impedance on resonance was much higher or much smaller than the bridge resistance. A simple two fluid model of the bridge-resonator circuit was developed and the size and shape of self-induced steps were calculated for a generalized Josephson oscillator relation I_S = I_c(l-q + q sin∫ 2e/hV dt) where q = 1 corresponds to the original Josephson relation and q = 1/2 represents the phase slip regime. At low critical currents (I_c < 10 µA) and low voltages (V < 3µV) the size and shape of experimentally observed self-induced steps agree with the q = 1 model. At higher voltages and/or critical currents the step size increasingly deviates from the q = 1 model towards q = 1/2. These observations are interpreted to indicate a progressive reduction of the amplitude of the oscillating Josephson supercurrent in proximity effect bridges from I_c towards I_c /2 as the critical current and/or voltage are increased.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Applied Physics
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Applied Physics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Mercereau, James E.
Thesis Committee:
  • Unknown, Unknown
Defense Date:5 March 1976
Record Number:CaltechTHESIS:12062011-081306612
Persistent URL:http://resolver.caltech.edu/CaltechTHESIS:12062011-081306612
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:6748
Collection:CaltechTHESIS
Deposited By: Dan Anguka
Deposited On:06 Dec 2011 17:00
Last Modified:26 Dec 2012 04:39

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