The Story Behind the Discovery of Superfluidity in Helium Three

  Douglas D. Osheroff  
Stanford University

The discovery of superfluidity in 3He had its origins at Los Alamos National Laboratory where Ed Hammel,  who was in charge of keeping their tritium source clean,  decided to liquify the 3He he had been collecting.  He published his resulting measurement of the 3He vapor pressure vs. temperature.  Thus began a world-wide study of this unusual Fermi fluid, for 3He atoms have a net spin of 1/2 and are therefore Fermi particles.  Speculation that liquid 3He might condense into a BCS superfluid was first published soon after the publication of the BCS theory in 1957, suggesting a superfluid transition temperature of order 80 mK.  Within a decade the Fermi-liquid properties of liquid 3He were well established,  but measurements down to 0.002K by John Wheatley's group at the University of Illinois found no evidence of a phase transition in the liquid.  When David Lee decided to use compressional cooling, first suggested by Pomeranchuk, to study 3He,  it was to look for nuclear spin ordering in the solid, not superfluidity in the liquid.  This lecture traces the series of events that led to the discovery of superfluidity in liquid 3He at 2:40 AM on April 20, 1972  in the basement of Clark Hall at Cornell Univerity.  I was there.