Quantum and quasiclassical types of superfluid turbulence

TL;DR

This paper investigates quantum and quasiclassical superfluid turbulence in helium-4, revealing decay behaviors, effective viscosity, and the generation of turbulence through ion injection and mechanical means.

Contribution

It provides new insights into the decay dynamics and effective viscosity of superfluid turbulence, and compares quantum and quasiclassical regimes.

Findings

Vortex line length decays as t^{-1} at low temperatures.

Effective kinematic viscosity is approximately 0.1 times the circulation quantum.

Ion injection can generate turbulence similar to mechanical methods at higher temperatures.

Abstract

By injecting negative ions in superfluid 4He in the zero-temperature limit (T < 0.5 K), we generated tangles of quantized vortex line with negligible large-scale flow. For this quantum regime of superfluid turbulence, the vortex line length L was found to decay at late time t as L proportional to t^{-1}; the prefactor being independent of the initial value of L. The corresponding effective kinematic viscosity is 0.1 kappa, where kappa is the circulation quantum. At T > 0.7 K, a jet of ions generates quasi-classical tangles identical to those produced by mechanical means.