A « supersolid » is a quantum solid inside which a fraction of the mass is superfluid. The coexistence of solid and superfluid properties is paradoxical and its understanding is a challenge attracting many research groups since its discovery in helium by Kim and Chan in 2004. The existence of anomalies in the rotational inertia of solid helium around 100 mK has been confirmed. They are accompanied by a peak in the specific heat and by astonishing anomalies in the elastic properties. It is now generally accepted that supersolidity is due to the presence of disorder in the samples: dislocations, grain boundaries, helium 3 impurities &However, in our opinion, nobody understands how which kind of disorder is responsible for the observed supersolidity. Although the characterization of disorder in solid helium samples is a difficult task, we have a long experience of crystal growth in helium and a dilution refrigerator with optical access which allows direct observation of the crystals during their growth, an essential control of their quality. We know how to prepare either polycrystals , disordered single crystals or very high quality single crystals. We propose to study the elastic properties and the rotational inertia of solid samples with known disorder. In most previous experiments one had to guess what was the crystal quality. With dc-flow experiments and ion mobility measurements, we also propose to investigate the predicted superfluidity of grain boundaries and dislocation networks. After clarifying the respective role of defects and impurities in solid helium, and thanks to the international collaboration we propose, we should be able to progress in the understanding of supersolidity, hopefully to discover its nature.
Field of science
- /agricultural sciences/agriculture, forestry, and fisheries/agriculture/grains and oilseeds
- /engineering and technology/materials engineering/crystals
Call for proposal
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