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Helium-3 superfluid discovery experiment 2026-10-18
David Morris Lee, Douglas Dean Osheroff and Robert Coleman Richardson compressed coexisting liquid and solid helium-3 in a cell precooled by a dilution refrigerator. Helium-4 pressure drove coupled bellows and a piston; a capacitance diaphragm gauge read pressure and platinum nuclear magnetic resonance supplied thermometry. Uniform compression revealed a slope break A and a small pressure drop B; decompression and varied solid fraction checked reproducibility. Their April 1972 paper, Evidence for a New Phase of Solid He3, interpreted a new solid phase, without establishing liquid superfluidity. [ref]
Evidence for a New Phase of Solid He3 by Douglas Dean Osheroff and others. 1972, pp.885–888, Figs.1–3
The October follow-up replaced the thermometer assembly with a sample nuclear magnetic resonance coil. An applied magnetic field gradient selected different sample layers, separating strong solid signals from the liquid background. At A the liquid resonance shifted; at B its shift disappeared and its magnetic susceptibility fell. Removing the gradient resolved the frequency shift directly. Independence from solid fraction and distinct relaxation times supported the liquid assignment. Thus the reinterpretation rested on phase-selective evidence, rather than relabeling the first paper's title. These magnetic observations identify changed liquid phases; they do not directly measure frictionless flow. [ref]
New Magnetic Phenomena in Liquid He3 below 3 mK by Douglas Dean Osheroff and others. 1972, pp.920–923, Figs.1–3
Douglas Dean Osheroff recalls the subsequent p-wave interpretation. [ref]
Superfluidity in 3He: Discovery and Understanding by Douglas Dean Osheroff. 1996 lecture, p.73
Compression and independent readout channels in the helium-3 superfluid discovery experiment
. Original functional diagram, not a reconstruction to scale. Left: drive, sample and pressure channel. Right: separate thermometer and sample nuclear magnetic resonance configurations; the latter replaces the former in the follow-up. Connections indicate function, not historical wiring. Details.
The inference has a useful limit. A pressure anomaly in two coexisting phases cannot, by itself, identify which phase changed: both contribute to the common phase coexistence curve. Thermometer lag, a temperature gradient or slow equilibration can also separate indicated temperature from the sample state. Correlating another response with the anomaly provides information that repeating the same pressure trace cannot supply. Conversely, a shifted magnetic resonance alone does not measure a frictionless flow rate.
Helium-3 superfluidity 2026-10-18
Helium-3 superfluidity involves Cooper pairs of fermions; helium-4 atoms are bosons. Individual helium-3 atoms do not undergo Bose-Einstein condensation. [ref]
The Extraordinary Phases of Liquid 3He by David Morris Lee. Lee, 1996 lecture; 1997 reprint pp.645–647
The helium-3 superfluid discovery experiment connects an unexpected pressure feature to a change in the state of a liquid. Its lesson is unusually instructive: finding a reproducible anomaly and identifying the material that changed are separate experimental achievements. Pomeranchuk cooling explains how the experiment reached its operating regime; an independent nuclear magnetic resonance channel distinguishes the phases.
Transverse nuclear magnetic resonance measures absorption from a radio-frequency magnetic field perpendicular to the static field. In the A phase, the resonance moved above the Larmor frequency; in the B phase it returned to that frequency despite the changed state. Anthony James Leggett connected the shift to collective spin-orbit structure. A predicted longitudinal resonance, driven parallel to the static field, supplied a further B-phase test.[ref]
Nobel Lecture: Superfluid 3He: the early days as seen by a theorist by Anthony James Leggett. pp.1002–1003 and1009, transverse geometry and longitudinal test
The helium-3 superfluid discovery experiment establishes why a new phase was inferred; comparing response channels then tests its internal structure. An unchanged peak in one geometry cannot, by itself, establish that nothing ordered.