The role of Helium-3 impurities in the stress induced roughening of superclimbing dislocations in solid Helium-4

TL;DR

This paper investigates how Helium-3 impurities influence the stress-induced roughening of superclimbing dislocations in solid Helium-4, revealing impurity activation energy's role in flow rate dips.

Contribution

It introduces a model linking Helium-3 impurity effects to dislocation roughening and flow rate behavior in solid Helium-4, highlighting impurity fraction's impact.

Findings

Flow rate dip temperature is set by impurity activation energy.

Dip width is mainly due to stress fluctuations, smaller than the dip temperature.

Impurity fraction logarithmically suppresses the dip temperature.

Abstract

We analyze the stress induced and thermally assisted roughening of a forest of superclimbing dislocations in a Peierls potential in the presence of Helium-3 impurities and randomly frozen in static stresses. It is shown that the temperature of the dip $T_d$ in the flow rate observed by Ray and Hallock (Phys.Rev. Lett. {\bf 105}, 145301 (2010)) is determined by the energy of the impurity activation from dislocation core. However, it is suppressed by, essentially, the logarithm of the impurity fraction. The width of the dip is determined by inhomogeneous fluctuations of the stresses and is shown to be much smaller than $T_d$.