By large-scale quantum Monte Carlo simulations we show that grain boundaries in 4He crystals are generically superfluid at low temperature, with a transition temperature of the order of ∼0.5 K at the melting pressure; nonsuperfluid grain boundaries are found only for special orientations of the grains. We also find that close vicinity to the melting line is not a necessary condition for superfluid grain boundaries, and a grain boundary in direct contact with the superfluid liquid at the melting curve is found to be mechanically stable and the grain-boundary superfluidity observed by Sasaki et al. [Science 313, 1098 (2006)] is not just a crack filled with superfluid.
Pollet, L; Boninsegni, M; Kuklov, A; Prokof'ev, Nikolai; Svistunov, Boris; and Troyer, M, "Superfluidity of Grain Boundaries in Solid 4He" (2007). Physics Department Faculty Publication Series. 1153.
Retrieved from https://scholarworks.umass.edu/physics_faculty_pubs/1153