Dr Jon Fenton
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- high-temperature superconductivity
- Josephson junctions
- low-temperature transport measurements
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Contact details:
Office: 2P1
Tel: +44 (0) 207 679 0640
Ext: 30640
Fax: +44 (0) 207 679 0595
Email: j.fenton ucl.ac.uk |
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Research interest
At present, I am working on an EPSRC-funded project to measure high-frequency quantum noise in resistively shunted Josephson junctions at temperatures below 1K in an update of a classic experiment by Koch et al. [1]. The aim is to provide a test of a theory regarding zero-point electromagnetic fluctuations as a candidate for dark energy, as suggested by Beck and Mackey [2]. I hope shortly to be making measurements on both NbN junctions (grown by our collaborators in Cambridge) and high-Tc cuprate junctions.
I have also been working on simulations of thermally activated processes in moderately damped junctions; this work has led to a paper, which has recently been published in Phys. Rev. B.
I previously developed a system for making low-temperature current-voltage measurements during focussed ion-beam milling (see Fig. 1 below). This system makes use of a liquid-helium cooled sample stage inside a dual-beam FIB microscope.
Recent publications
- Monte Carlo simulations of thermal fluctuations in moderately damped Josephson junctions: Multiple escape and retrapping, switching- and return-current distributions and hysteresis, J.C. Fenton and P.A. Warburton, Phys. Rev. B 78 054526 (2008) [PDF] © APS.
- Skewness variations of switching-current distributions in moderately damped Josephson junctions due to thermally induced multiple escape and retrapping, J.C. Fenton and P.A. Warburton, accepted for publication in the proceedings of the LT25 conference (2008). [PDF] © IOP Publishing Ltd.
- Switchable phase diffusion in intrinsic Josephson junction arrays, J.C. Fenton, M. Korsah, C.R.M. Grovenor and P.A. Warburton, Physica C 460 1407 (2007). [PDF] © Elsevier Science
- Critical current suppression in sub-micron intrinsic Josephson junction arrays, J.C. Fenton, M. Korsah, C.R.M. Grovenor and P.A. Warburton, J. Phys.: Conf. Ser. 43 1114 (2006). [PDF] © IOP Publishing Ltd.
- Josephson current suppression in three-dimensional focused-ion-beam fabricated sub-micron intrinsic junctions,
P.A. Warburton, J.C. Fenton, M. Korsah, C.R.M. Grovenor, Superconductor Science & Technology 19 (5): S187-S190 (2006). [PDF] © IOP Publishing Ltd.
- Heating in mesa structures, J.C. Fenton and C.E. Gough, J. Appl. Phys. 94 4665 (2003). [PDF] © American Institute of Physics
- System for fast time-resolved measurements of c-axis quasiparticle conductivity in intrinsic Josephson junctions of 2212-BSCCO, J.C. Fenton, P.J. Thomas, G. Yang and C.E. Gough, Appl. Phys. Lett. 80 2535 (2002). [PDF] © American Institute of Physics
- Time dependence of current-voltage measurements of c-axis quasiparticle conductivity in 2212-BSCCO mesa structures, J.C. Fenton, G. Yang and C.E. Gough, Physica C 388 341 (2003). [PDF] © Elsevier Science
Biography
2004-present: Research Fellow in Electronic & Electrical Engineering, UCL and LCN
2002-2004: Research Associate in Physics, University of Birmingham
2002: PhD in Condensed Matter Physics from University of Birmingham
1998: BA, MSci in Natural Sciences (Experimental and Theoretical Physics) from University of Cambridge
Research
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Figure 1. Variation of cold-stage IV with increasing milling time (uppermost points correspond to most milling), showing the development of Josephson junctions. The top inset shows a top view of the milling configuration (2micron scale box). The bottom inset shows an oblique side view of a completed device. Circled is the central region, in which applied current flows perpendicular to the layers, through the intrinsic Josephson junctions.
Click on the image to see a larger version.
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