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| VOLUME 26 (1977) | ISSUE 3 |
PAGE 183
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Vacancy mobility in crystalline He3
Iordanskii S.V.
Vacancies that are delocalized at low temperatures in crystalline He3 give rise to indirect exchange, since the circuiting of the vacancy around a closed path is equivalent to a permutation of atoms, and consequently, an important role in the calculation of the energy is played by the symmetry of the wave function, i.e. , its dependence on the spins. Actually the direct exchange in He3 is extremely small, J~10"3 K, whereas the vacancy mobility is quite large. According to various estimates, the corresponding width of the band is Δ~10 K, so that there exists a temperature region where direct exchange can be neglected.
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![](/ps/1375/article_20850_800_head.png "Vacancies that are delocalized at low temperatures in crystalline He<sup>3</sup> give rise to indirect exchange, since the circuiting of the vacancy around a closed path is equivalent to a permutation of atoms, and consequently, an important role in the calculation of the energy is played by the symmetry of the wave function, i.e. , its dependence on the spins. Actually the direct exchange in He<sup>3</sup> is extremely small, J~10"<sup>3</sup> K, whereas the vacancy mobility is quite large. According to various estimates, the corresponding width of the band is Δ~10 K, so that there exists a temperature region where direct exchange can be neglected.")