Possible role of 3He impurities in solid 4He
  We use a quantum lattice gas model to describe essential aspects of the motion of 4He atoms and of 3He impurities in solid 4He. This study suggests that 3He impurities bind to defects and promote 4He atoms to interstitial sites which can turn the bosonic quantum disordered crystal into a metastable supersolid. It is suggested that defects and interstitial atoms are produced during the solid 4He nucleation process where the role of 3He impurities (in addition to the cooling rate) is known to be important even at very small (1 ppm) impurity concentration. It is also proposed that such defects can form a glass phase during the 4He solid growth by rapid cooling. 
Efstratios Manousakis