Measurement of the kinetic energy and lattice constant in hcp solid helium at temperatures 0.07-0.4 K.
The single atom kinetic energy kappa of high purity solid hcp 4He has been measured by neutron Compton scattering, at temperatures between 0.07 and 0.4 K and a pressure of 40 bar. Within statistical error of approximately 2% no change in kappa was observed. The values of kappa at approximately 0.07 K were the same in a single crystal and a polycrystalline sample and were also unaffected (within statistical error) by the addition of 10 ppm of 3He. The lattice constant was also found to be independent of temperature to within 1 part in 2000. These results suggest that the supersolid transition in 4He has a different microscopic origin to the superfluid transition in the liquid.
Adams
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ISIS Facility, Rutherford Appleton Laboratory, Chilton OX11 0QX, United Kingdom.
Mayers
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Kirichek
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Down
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