Absence of off-diagonal long-range order in hcp $^{\bf 4}$He dislocation cores

TL;DR

This study uses quantum simulations to investigate dislocation cores in hcp $^4$He, finding no evidence of superfluidity or off-diagonal long-range order, thus challenging previous interpretations of mass transport phenomena.

Contribution

It provides the first detailed quantum simulation analysis showing the absence of superfluidity in dislocation cores of hcp $^4$He, contradicting earlier superfluid dislocation network hypotheses.

Findings

Bose-Einstein condensate fraction is effectively zero in dislocation cores

Dislocation cores do not exhibit off-diagonal long-range order

Results challenge the superfluid dislocation network interpretation

Abstract

The mass transport properties along dislocation cores in hcp $^4$He are revisited by considering two types of edge dislocations as well as a screw dislocation, using a fully correlated quantum simulation approach. Specifically, we employ the zero-temperature path-integral ground state (PIGS) method together with ergodic sampling of the permutation space to investigate the fundamental dislocation core structures and their off-diagonal long-range order properties. It is found that the Bose-Einstein condensate fraction of such defective $^4$He systems is practically null ($\le 10^{-6}$), just as in the bulk defect-free crystal. These results provide compelling evidence for the absence of intrinsic superfluidity in dislocation cores in hcp $^4$He and challenge the superfluid dislocation-network interpretation of the mass-flux-experiment observations, calling for further experimental investigation.