A New Phenomenon in the Supraconducting Transition of Tantalum and of Tin

Abstract

THE transition from the supraconducting to the normal resisting state under certain conditions is found not to be continuous but to include a hitherto unsuspected spontaneous increase in resistance followed by a slower decrease. The spontaneous decrease in resistance usually proceeds for several minutes in a succession of steps, until only a fraction of its crest value remains. This crest value of the transient resistance is sometimes 75 per cent of the normal. After such an effect has occurred, it will not occur again when the same conditions are re-established, unless in the meantime the temperature has been lowered or else a time interval of at least half an hour has elapsed.