The 80th Birthday of Brian Josephson
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The 80th Birthday of Brian Josephson John Rowell 1
# Springer Science+Business Media, LLC, part of Springer Nature 2020
Dear Brian, Congratulations on your 80th birthday. Rumors of your proposals of “possible new effects” began to circulate at Bell Labs during the summer of 1962 and became more specific with the return of Phil Anderson from his year at Cambridge. They were not met with universal acceptance, especially by theorists! I was not able to attend the conference in London that summer, when you and John Bardeen exchanged your differing viewpoints on the reality of pair tunneling. Instead, my wife and I visited most of the National Parks from Vancouver to Arizona. My interest in tunneling at Bell was due to the availability in the department of equipment that generated plots of the slope of current-voltage characteristics. It had been built by Don Thomas, Alan Chynoweth, and Ralph Logan for their studies of semiconductor diodes. The invention of the lock-in amplifier a few years later made such plots much easier to obtain. Following the fabrication processes described by Ivar Giaever, I began to make Al/AlOx/Pb junctions in 1962. On January 3 of 1963, I decided to measure one such junction in the only cryostat at Bell that reached well below 1 K. It was being used by Ted Geballe, Bernd Matthias, and Ernie Corenzwit in their search for new superconductors. Even at close to 0.3 K, we saw
* John Rowell [email protected] 1
Bell Telephone Laboratories, Murray Hill, New Jersey, USA
nothing unusual in the I–V characteristic. In hindsight, the junction resistance was too high, and the noise in that laboratory was large. Phil was surprised that we had not seen a supercurrent but then proposed the notion of a coupling energy which had to be large, implying that we needed junctions with lower resistances. Aluminum oxidizes so rapidly in laboratory air that the required short exposure of the film was difficult to achieve by venting a conventional evaporator. During 1962, I had made a few junctions using oxidized tin as the base film, but their resistances were not reproducible. However, tin was an obvious choice, as its Tc of 3.7 K meant that a junction of Sn/SnOx/Pb would be fully superconducting well above 1 K, which was the limit of my cryostat at the time. On January 21, 1963, Len Kopf, my TA (Technical Assistant), assembled the apparatus sketched on page 37 of my laboratory notebook. It allowed oxidation of the tin film in dry oxygen at a certain temperature. The events of the day are then described in some detail (Making notebook entries each day was strongly encouraged at Bell, in case something “patentable” was achieved). The first junctions Len made were all good and had the hoped for low resistances.
J Supercond Nov Magn
J Supercond Nov Magn
I observed a “peculiar low resistance at the origin.” Your prediction of “novel” had become “peculiar.” I observed that the small current was destroyed by moving a bar magnet near to the dewar; I even used a horseshoe magnet as well. I must have had both magn
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