Drift mechanism of the metal nanowires formation in liquid helium

Abstract

It is shown theoretically that the mechanism of the rapid coagulation of metal nanospheres into a nanowire in a quantum vortex proposed by E. B. Gordon et al. (Low Temp. Phys., 2010, 36, 590) could not be realized, due to the enormous heat release expelling the nanospheres from the vortex. Also, Gordon's hypothesis on nanowire formation in quantum vortices contradicts the observations that nanowires form above the λ-point (where no quantum vortices exist) and on superfluid helium's surface (parallel to it), which is always perpendicular to the quantum vortices. The nanowire formation process in bulk and dropwise liquid helium is described as a special case of aggregation controlled by diffusion in an external electric field. The nanosphere charging occurs due to the thermoelectric emission from their overheating and also laser ablation. The charged nanospheres attract neutral ones to minimize the electrostatic energy and are also attracted to elevations (field concentrators) on the conductive surfaces surrounding the experimental volume. Both processes lead to nanowire formation and drift prevails over diffusion in both cases. The described mechanism leads to the formation of self-similar anisometric structures in agreement with experimental data.