What did scientists discover?
In a metal alloy (think brass, bronze or steel), two or more elements, under the right conditions, mix thoroughly to create a new material. In this experiment, scientists took two isotopes of helium (3He, with one neutron, and 4He, with two) and mixed them under the right conditions (under pressure and at ultra-low temperatures) to create a solid. When they dropped the thermostat even further, the two isotopes separated, forming some regions in the solid that were almost pure 3He. The researchers measured the temperatures at which these phase separations occurred down to extremely low 3He concentrations.
Why is this important?
Similar phase separations occur in ordinary metal alloys, as well. But the atoms move so slowly that the transitions last for eons — literally — making them impossible to measure.
In these helium experiments, however, the phase separation occurs quickly, on the quantum level, as subatomic particles zip through barriers — so-called quantum tunneling. Scientists can use this faster, quantum phase separation to understand the analogous classical process occurring in metal alloys. This experiment is also the first observation of transitions for such low 3He concentrations — below a few hundred parts per million (ppm).
Who did the research?
D. Candela1, B. P. Cowan2, C. Huan3, S. S. Kim3, L. Yin3, J. S. Xia3 and N.S. Sullivan3
1University of Massachusetts; 2Royal Holloway College, London; 3University of Florida
Why did they need the MagLab?
The unique ultra-low temperature instrumentation of the MagLab’s High B/T Facility was critical for these measurements. The low temperature electronics provided the sensitivity required to observe samples with 3He concentrations as low as 16 ppm.
Details for scientists
- View or download the expert-level Science Highlight, Phase separation of very dilute concentrations of 3He in Solid 4He
This research was funded by the following grants: G.S. Boebinger (NSF DMR-1157490); N. Sullivan (NSF-DMR-1303599)
For more information, contact Neil Sullivan.