Condensed Matter Physics Seminar

Dr Dmitriy Zmeev, Lancaster University

Friday 20 November 2015, 1500-1600
Furness Lecture Theatre 2

Dissipation of quasiclassical quantum turbulence in superfluid 4He - Turbulence is a common state of flow in fluids. So far, satisfactory understanding is only achieved for homogeneous and isotropic turbulence in classical fluids. Chaotic large-scale motion of topological defects (vortices) in superfluids is surprisingly very similar to turbulence in a classical fluid. We report observations of homogeneous and isotropic turbulence decay in 4He in the limit of low temperatures. We compare the decay of turbulence produced by a moving grid to the decay of turbulence created by either impulsive spin-down to rest or by intense ion injection. In all cases, the vortex line density L decays at late time t as L~t^(-3/2). Below 0.8 K, the spin-down turbulence maintains initial rotation and decays slower than grid turbulence and ion-jet turbulence. This may be due to a decoupling of the large-scale superfluid flow from the normal component at low temperatures, which changes its effective boundary condition from no-slip to slip.