Supersolid

The Suprasolidität is a quantum mechanical state of matter, which simultaneously displays both properties of solid and superfluid body. Suprasolidität can be observed at very high pressures and very low temperatures, when quantum mechanical phenomena come into play. This state was predicted both by David J. Thouless and by Alexander Andreev and Evgeny Mikhailovich Lifshitz in 1969. A first experimental evidence of a superconducting solid state succeeded Eun- Seong Kim and Moses HW Chan on the example of ultrakaltem solid helium -4 ( 4He ).

Properties

The experiments of Eun- Seong Kim and Moses HW Chan at the Pennsylvania State University with 4He at temperatures below 200 mK by a torsional oscillator provided the first experimental evidence for the existence of Suprasolidität. In this experiment, 4He moved when cooled to below about 200 mK not like a classic solid but showed a rotation anomaly, which is comparable to that of superfluid 4He. Paradoxically, is connected to the partial passage in the superfluid state, an increase in stiffness of the material. Measurements of the specific heat at the transition point to the rotation anomaly indicate a real phase transition.

Theory

As a possible cause vacancies in 4He crystals are considered. It is discussed whether these crystal defects essential also exist at absolute zero, or whether they are based on experimentally used imperfect crystals. At sufficiently low temperatures the atoms are in supra solid bodies such as the Bose -Einstein condensate by superposition of their wave functions, and thus the vacancies in the crystal delocalized ( quantum crystal). The Suprasolidität represents thus analogous to the Bose gas and superfluidity a form of Bose -Einstein condensate.

Following the initial observation of the Suprasolidität other possible causes in the journals were hotly debated and controversial. An alternative explanation was not fully excludable impurities with 3He in the ppb range, which is responsible for the superfluidity, while the crystalline structure is found only in the 4He species. A simultaneous occurrence of both phases ( superfluid and solid) in the same atomic species would not be given.