Possible role of 3He impurities in solid 4He

TL;DR

This paper models how 3He impurities in solid 4He can bind to defects and promote the formation of interstitial atoms, potentially leading to a metastable supersolid phase, especially during rapid cooling and nucleation.

Contribution

It introduces a quantum lattice gas model to explore the role of 3He impurities in defect formation and supersolidity in solid 4He, highlighting impurity effects at very low concentrations.

Findings

3He impurities bind to defects in solid 4He.

Impurities promote interstitial atom formation, possibly inducing supersolidity.

Defects may form a glass phase during rapid cooling.

Abstract

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.