Related papers: Classical rotational inertia of solid helium 4
Helium films show various quantum phases that undergo quantum phase transitions by changing coverage n. We found anomalous elastic phenomena in bosonic 4He and fermionic 3He films adsorbed on a glass substrate. The films stiffen under AC…
Although solid helium-4 (4He) may be a supersolid it also exhibits many phenomena unexpected in that context. We studied relaxation dynamics in the resonance frequency f(T) and dissipation D(T) of a torsional oscillator containing solid…
We demonstrate the instability of the free surface of a soft elastic solid facing downwards. Experiments are carried out using a gel of constant density $\rho$, shear modulus $\mu$, put in a rigid cylindrical dish of depth $h$. When turned…
Kim and Chan have recently observed Non-Classical Rotational Inertia (NCRI) for solid $^4$He in Vycor glass, gold film, and bulk. Their low $T$ value of the superfluid fraction, $\rho_{s}/\rho\approx0.015$, is consistent with what is known…
We present a superfluid hydrodynamic model for the increase in moment of inertia, $\Delta I$, of molecules rotating in liquid $^4$He. The static inhomogeneous He density around each molecule (calculated using the Orsay-Paris liquid $^4$He…
The rotational property of a quantum liquid at the vicinity of the lambda point is examined. In a liquid helium 4 just above the lambda point, under the strong influence of Bose statistics, the coherent many-body wave function grows to an…
We report on experimental confirmation of the non-classical rotational inertia (NCRI) in solid helium samples originally reported by Kim and Chan. The onset of NCRI was observed at temperatures below ~400 mK. The ac velocity for initiation…
By large-scale quantum Monte Carlo simulations we show that grain boundaries in Helium-4 crystals are generically superfluid at low temperature, with a transition temperature of the order of ~0.5K at the melting pressure; insulating grain…
We study the effect of confinement on solid 4-He's nonclassical rotational inertia (NCRI) in a torsional oscillator by constraining it to narrow annular cells of various widths. The NCRI exhibits a broad maximum value of 20% for annuli of…
We present the results of an experimental investigation into buoyant rigid spheres rising through highly concentrated collections of hydrated hydrogel particles. The volume fraction of particles is such that the mechanical properties of the…
We show that the presumed wavy roughness distributed along the wall of different nanopores (radius : a around 3.5 nm for Vycor or a silica glass; around 245 nm for porous gold) will induce larger volume flow rates of solid helium (of which…
It is shown that a suspension of particles in a partially-filled, horizontal, rotating cylinder is linearly unstable towards axial segregation and an undulation of the free surface at large enough particle concentrations. Relying on the…
We have measured a precessing superfluid vortex line, stretched from a wire to the wall of a cylindrical cell. By contrast to previous experiments with a similar geometry, the motion along the wall is smooth. The key difference is probably…
This study investigates the nonlinear stability and dynamics of gravity-driven viscous films on a vertical rotating cylinder, considering both outer and inner surface flows with slip conditions at the cylinder wall. We develop an asymptotic…
We consider superfluid helium inside a container which rotates at constant angular velocity and investigate numerically the stability of the array of quantized vortices in the presence of an imposed axial counterflow. This problem was…
The elastic properties of hcp $^4$He samples have been shown to display various anomalies. The elastic shear modulus stiffens and the moment of rotational inertia drops when the temperature is lowered below $\sim$ 0.2 K. The relation…
The flow velocity of solid 4He through a porous membrane frozen into a crystal has been measured in the temperature interval 0.1 - 1.8 K. A flat capacitor consisting of a metalized plastic porous membrane and a bulk electrode is applied and…
A density functional theory is used to investigate the instability arising in superfluid $^4$He as it flows at velocity u just above the Landau critical velocity of rotons v_c. Confirming an early theoretical prediction by one of us [JETP…
Recent experiments showed that the shear modulus of solid 4He stiffens in the same temperature range (below 200 mK) where mass decoupling and supersolidity have been inferred from torsional oscillator measurements. The two phenomena are…
Probing the fluid dynamics of thin films is an excellent tool to study the solid/liquid boundary condition. There is no need for external stimulation or pumping of the liquid due to the fact that the dewetting process, an internal…