Showing papers by "Vladimir Eltsov published in 2014"
TL;DR: In this article, the normal component interacts with the superfluid component via mutual friction, which damps the motion of quantized vortex lines and eventually couples the liquid component to the container.
Abstract: In Fermi superfluids, such as superfluid 3He, the viscous normal component can be considered to be stationary with respect to the container. The normal component interacts with the superfluid component via mutual friction, which damps the motion of quantized vortex lines and eventually couples the superfluid component to the container. With decreasing temperature and mutual friction, the internal dynamics of the superfluid component becomes more important compared with the damping and coupling effects from the normal component. As a result profound changes in superfluid dynamics are observed: the temperature-dependent transition from laminar to turbulent vortex motion and the decoupling from the reference frame of the container at even lower temperatures.
22 citations
TL;DR: In this paper, the authors used the dependence of the relaxation rate on the density of thermal quasiparticles to implement thermometry in the Bose-Einstein condensates of magnons.
Abstract: Coherent precession of trapped Bose–Einstein condensates of magnons is a sensitive probe for magnetic relaxation processes in superfluid $$^3$$
He-B down to the lowest achievable temperatures. We use the dependence of the relaxation rate on the density of thermal quasiparticles to implement thermometry in $$^3$$
He-B at temperatures below $$300\,\upmu $$
K. Unlike popular vibrating wire or quartz tuning fork based thermometers, magnon condensates allow for contactless temperature measurement and make possible an independent in situ determination of the residual zero-temperature relaxation provided by the radiation damping. We use this magnon-condensate-based thermometry to study the thermal impedance of the interface between A and B phases of superfluid $$^3$$
He. The magnon condensate is also a sensitive probe of the orbital order-parameter texture. This has allowed us to observe for the first time the non-thermal signature of the annihilation of two AB interfaces.
15 citations
TL;DR: In this paper, the authors measured the decay of ground state condensates after switching off the pumping in the temperature range (0.14÷0.2)T c. The measured dependence of the relaxation on the shape of the trapping potential is in good agreement with their calculations based on the magnetic field profile and the magnon modified texture.
Abstract: In superfluid 3He-B externally pumped quantized spin-wave excitations or magnons spontaneously form a Bose-Einstein condensate in a 3-dimensional trap created with the order-parameter texture and a shallow minimum in the polarizing field. The condensation is manifested by coherent precession of the magnetization with a common frequency in a large volume. The trap shape is controlled by the profile of the applied magnetic field and by the condensate itself via the spin-orbit interaction. The trapping potential can be experimentally determined with the spectroscopy of the magnon levels in the trap. We have measured the decay of the ground state condensates after switching off the pumping in the temperature range (0.14÷0.2)T
c. Two contributions to the relaxation are identified: (1) spin diffusion with the diffusion coefficient proportional to the density of thermal quasiparticles and (2) the approximately temperature-independent radiation damping caused by the losses in the NMR pick-up circuit. The measured dependence of the relaxation on the shape of the trapping potential is in a good agreement with our calculations based on the magnetic field profile and the magnon-modified texture. Our values for the spin diffusion coefficient at low temperatures agree with the theoretical prediction and earlier measurements at temperatures above 0.5T
c.
15 citations
TL;DR: In this paper, the authors used the dependence of the relaxation rate on the density of thermal quasiparticles to implement thermometry in 3He-B at temperatures below 300 $\mu$K.
Abstract: Coherent precession of trapped Bose-Einstein condensates of magnons is a sensitive probe for magnetic relaxation processes in superfluid 3He-B down to the lowest achievable temperatures. We use the dependence of the relaxation rate on the density of thermal quasiparticles to implement thermometry in 3He-B at temperatures below 300 $\mu$K. Unlike popular vibrating wire or quartz tuning fork based thermometers, magnon condensates allow for contactless temperature measurement and make possible an independent in situ determination of the residual zero-temperature relaxation provided by the radiation damping. We use this magnon-condensate-based thermometry to study the thermal impedance of the interface between A and B phases of superfluid 3He. The magnon condensate is also a sensitive probe of the orbital order-parameter texture. This has allowed us to observe for the first time the non-thermal signature of the annihilation of two AB interfaces.
15 citations
TL;DR: In this paper, the Andreev reflection of quasiparticle excitations from quantized line vortices is reviewed in the isotropic B phase of superfluid 3He in the temperature regime of ballistic QP transport at T ≤ 0.20T.
Abstract: Andreev reflection of quasiparticle excitations from quantized line vortices is reviewed in the isotropic B phase of superfluid 3He in the temperature regime of ballistic quasiparticle transport at T ≤ 0.20T
c
. The reflection from an array of rectilinear vortices in solid-body rotation is measured with a quasiparticle beam illuminating the array mainly in the orientation along the rotation axis. The result is in agreement with the calculated Andreev reflection. The Andreev signal is also used to analyze the spin-down of the superfluid component after a sudden impulsive stop of rotation from an equilibrium vortex state. In a measuring setup where the rotating cylinder has a rough bottom surface, annihilation of the vortices proceeds via a leading rapid turbulent burst followed by a trailing slow laminar decay, from which the mutual friction dissipation can be determined. In contrast to the currently accepted theory, it is found to have a finite value in the zero-temperature limit: α(T→0) = (5 ± 0.5) × 10−4.
4 citations
TL;DR: In this paper, the Andreev reflection of quasiparticle excitations from quantized line vortices is reviewed in the isotropic B phase of superfluid and the spin down of the superfluid component after a sudden impulsive stop of rotation from an equilibrium vortex state.
Abstract: Andreev reflection of quasiparticle excitations from quantized line vortices is reviewed in the isotropic B phase of superfluid $^3$He in the temperature regime of ballistic quasiparticle transport at $T \leq 0.20\,T_\mathrm{c}$. The reflection from an array of rectilinear vortices in solid-body rotation is measured with a quasiparticle beam illuminating the array mainly in the orientation along the rotation axis. The result is in agreement with the calculated Andreev reflection. The Andreev signal is also used to analyze the spin down of the superfluid component after a sudden impulsive stop of rotation from an equilibrium vortex state. In a measuring setup where the rotating cylinder has a rough bottom surface, annihilation of the vortices proceeds via a leading rapid turbulent burst followed by a trailing slow laminar decay from which the mutual friction dissipation can be determined. In contrast to currently accepted theory, mutual friction is found to have a finite value in the zero temperature limit: $\alpha (T \rightarrow 0) = (5 \pm 0.5) \cdot 10^{-4}$.
2 citations