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The Manchester rotating cryostat has been used to measure the longitudinal and transverse coefficients of vortex mutual friction in the A and B phases of superfluid3He. In the B phase the dominant contribution to the mutual friction is scattering of excitations off occupied bound states in the vortex core. The A phase results are explained quantitatively by assuming that doubly quantised continuous vortices are created with a dynamics determined by the equation of motion of the orbital vectorI; the measurements enable us to put an upper limit on the orbital inertia of less than 0.01h per Cooper pair. History-dependent textural effects which had to be overcome in order to make meaningful measurements in the A phase are explained by noting that for a given rotation direction the most stable vortices can be formed more easily from one direction of uniformI texture than the other.  相似文献   

3.
Volovik  G. E. 《JETP Letters》2022,115(5):276-279
JETP Letters - Recently, a new topological phase of superfluid 3He called the β phase has been obtained by strong polarization of the nematic polar phase. We consider half-quantum vortices,...  相似文献   

4.
M. A. Zubkov 《JETP Letters》2017,105(11):721-726
We discuss the polar phase of 3He, which is realized in the anisotropic aerogel. We consider it in the framework of the BCS model. In the absence of the spin–orbit interaction, this model predicts the appearance of the Fermi line. However, it is topologically unstable. We demonstrate that the spin–orbit interaction gives rise to the appearance of the two Fermi points instead of the Fermi line. In addition to the gapless Nambu–Goldstone bosons in this system the collective gapped bosonic states exist. Their gaps are calculated, and the corresponding Nambu sum rule is established.  相似文献   

5.
During studies of the impact of single neutrons on superfluid3He at around 100μK we have measured the thermal energy released in the superfluid following the nuclear reaction, n+3He→p+3H+764keV. However, we find that the measured energy deposited in the quasiparticle system shortly after this reaction is substantially less than what we expect. We believe that this energy deficit represents that energy which has gone into the creation of vortices, in analogy to the creation of cosmic strings in the early universe via the Kibble mechanism. Furthermore, from the magnitude of the deficit, we can infer the vortex density which compares favorably with that predicted in Zurek’s scenairo.  相似文献   

6.
We report results of low frequency nuclear magnetic resonance (NMR) experiments in the superfluid polar phase of 3He, which is stabilized by a new type of “nematic” aerogel—nafen. We have found that an interaction between transverse and longitudinal NMR modes may essentially influence the spin dynamics. Theoretical formulas for NMR resonant frequencies are derived and applied for interpretation of the experimental results.  相似文献   

7.
The kinetics of the sorption and subsequent desorption of gaseous 3He in a C60 fullerite powder has been studied in the temperature range of 2–292 K. The temperature dependences of the diffusion coefficients of 3He and 4He impurities in fullerite have been plotted using the measured characteristic times of filling of octahedral and tetrahedral interstices, as well as previous data. These temperature dependences of the diffusion coefficients of 3He and 4He impurities in fullerite are qualitatively similar. A decrease in the temperature from 292 to 79 K is accompanied by a decrease in the diffusion coefficients, which corresponds to the dominance of the thermally activated diffusion of helium isotopes in fullerite. A further decrease in the temperature to 8–10 K leads to an increase in the diffusion coefficients by more than an order of magnitude. The diffusion coefficients of 3He and 4He are independent of the temperature below 8 K, indicating the tunnel character of the diffusion of helium in C60 fullerite. The isotope effect is manifested in the difference between the absolute values of the diffusion coefficients of 3He and 4He atoms at the same temperatures.  相似文献   

8.
It has been shown that, in the Landau gauge of the SU(2) Yang-Mills theory, the residual global symmetry supports the existence of topological vortices which resemble disclination defects in nematic liquid crystals and Alice (half-quantum) vortices in superfluid 3He in the A-phase. The theory also possesses half-integer and integer-charged monopoles, which are analogous to the point-like defects in nematic crystal and in liquid helium. We argue that the deconfinement phase transition in the Yang-Mills theory in the Landau gauge is associated with the proliferation of these vortices and/or monopoles. The text was submitted by the author in English.  相似文献   

9.
A new method for studying the processes of the establishment of the thermodynamic equilibrium in the adsorbed 3He layers in highly porous media has been proposed. Using this method, the thermalization of adsorbed 3He on silica aerogel at a temperature of 1.5 K has been studied. The process of the establishment of the thermodynamic equilibrium has been controlled by measuring the pressure in an experimental cell, the amplitude of the NMR signal, and the nuclear spin-spin and spin-lattice relaxation times of adsorbed 3He. It has been shown that the establishment of the thermodynamic equilibrium in the adsorbed 3He-aerogel system is characterized by a time of 26 min.  相似文献   

10.
The properties of liquid 3He in a low-density aerogel preliminarily covered with a few monolayers of 4He were studied by pulsed and nonlinear CW NMR techniques. It was found that an NMR frequency shift from the Larmor value exhibits a sharp increase at a magnetization tilting angle exceeding 104°. Nonlinear CW NMR signals related to the formation of a macroscopic region featuring homogeneous precession of the magnetization (homogeneous precession domain) were observed. The experimental results confirm that the low-temperature superfluid 3He phase in the aerogel is analogous to the B-phase in bulk 3He and indicate that the spin supercurrents play an important role in the spin dynamics of superfluid 3He in aerogel.  相似文献   

11.
In a smooth-walled rotating container vortices nucleate spontaneously in3He-B at a critical velocityv c (T, P) which is related to the bulk superflow instability velocityv cb (T, P). This process takes place at the wall of the container. Vortices are also observed to nucleate at lower velocities in the bulk liquid in ionizing radiation. For this thermal neutrons are most practical since for them the absorption cross section is large in3He. An absorption event creates local overheating, a hot bubble in the cold superflow. An increasing number of vortex rings is observed to emerge from the bubble as a function of the superflow velocity.  相似文献   

12.
Experimental data on the momentum distributions of 4He nuclei originating from 6He and 6Li breakup on various targets are presented over a wide beam energy range. The experiment with 6He was performed at the DRIBs accelerator complex for radioactive beams at the Joint Institute for Nuclear Research (JINR, Dubna). The intensity of the 6He beam used was 5 × 106 particles per second and its energy was 10 MeV per nucleon. The momentum distributions of breakup products were measured by means of the MSP-144 magnetic spectrometer. The distribution width was shown to be virtually independent of the target mass. A small value of this width, σ ~ 28 MeV/c, confirms the presence of a halo in 6He. The measurements performed with 6Li beams of energy 18 and 46 MeV per nucleon at the U-400M accelerator yielded a width value of σ ~ 50 MeV/c for the momentum distributions of 4He nuclei, which is intermediate between that for 6He and those for stable nuclei. A compilation of the widths of the momentum distributions of fragments originating from the breakup of various nuclei is presented versus the binding energy of one or two neutrons in these nuclei, the target mass and the projectile energy.  相似文献   

13.
We discuss the effective metric experienced by the Nambu–Goldstone mode propagating in the broken symmetry spin-superfluid state of coherent precession of magnetization. This collective mode represents the phonon in the RF driven or pulsed out-of-equilibrium Bose–Einstein condensate (BEC) of optical magnons. We derive the effective BEC free energy and consider the phonon spectrum when the spin superfluid BEC is formed in the anisotropic polar phase of superfluid 3He, experimentally observed in uniaxial aerogel 3He-samples. The coherent precession of magnetization experiences an instability at a critical value of the tilting angle of external magnetic field with respect to the anisotropy axis. From the action of quadratic deviations around equilibrium, this instability is interpreted as a Minkowski-to-Euclidean signature change of the effective phonon metric. We also note the similarity between the magnon BEC in the unstable region and an effective vacuum scalar “ghost” condensate.  相似文献   

14.
The results of searching for production of superheavy hydrogen isotopes 4,5H in reactions of absorption of stopped π? mesons by 10,11B nuclei are reported. A peak near 3 MeV was observed in the missing mass spectra measured in the reactions 10,11B(π?, t4He)X, 10B(π?, d4He)X, and 10B(π?, t3He)X. A structure caused by two 5H states with the resonance energies E R = 5.2 and 10.4 MeV was observed in the missing mass spectra measured in the reactions 11B(π?, d4He)X, 11B(π?, t3He)X, and 10B(π?, d3He)X.  相似文献   

15.
In this paper, the cross section of the 4He + 64Zn and 6He + 64Zn reactions, at bombarding energies above and below the fusion barrier, has been investigated. Soft-core nucleon-nucleon interaction and the Monte Carlo method have been employed for studying the nuclear potential of the projectile-target system. One adjustable parameter has been chosen in this study. This parameter can change the depth of the soft-core potential. It has to be adjusted so that the calculated elastic scattering and fusion cross sections are in acceptable agreement with experimental data. Our results indicate that an increase in energy decreases the depth parameter of the soft-core nucleon-nucleon potential obtained from careful analysis the 4He + 64Zn and 6He + 64Zn reactions. Likewise, by comparing the results obtained from both reactions, one can observe that the calculated depth parameter for the reaction related to 6He is larger than that for 4He at the same energy, in particular at the sub-barrier energies. We try to explain this behavior.  相似文献   

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The pygmy-resonance parameters and the E1 strength function are derived for 208Pb using a fully self-consistent microscopic formalism recently developed for magic nuclei, which takes into account quasiparticle phonon interactions (or coupling to phonons) in addition to the random phase approximation. For the radiative strength function of 208Pb at energies above 5 MeV, the experimental data of the Oslo group are adequately described by our predictions, whereby the important role of coupling to phonons is confirmed. By comparing the measurements based on the (3He, 3He′γ) and (γ, γ′) reactions, we discuss the physical properties of the radiative strength function measured for 208Pb. For the neutron-rich 70Ni nucleus, predictions for the radiative strength function and the pygmy resonance are obtained using a partially self-consistent approach, which invokes the Skyrme forces in deriving the mean field, effective nucleon–nucleon interaction, and phonon characteristics.  相似文献   

19.
Experimental cross sections of formation of isotopes 46Sc (in reaction 6He + 45Sc), 196,198Au (in reaction 6He + 197Au), and 65Zn (in reaction 6He + 64Zn) are analyzed. The time-dependent Schrödinger equation for the outer neutrons of 6He and 197Au nuclei is solved numerically to calculate the probability of neutron transfer and transfer cross sections. In reaction 6He + 197Au, the contribution of fusion and subsequent evaporation to experimental data can be neglected, while the corresponding contributions to reactions 6He + 45Sc and 6He + 64Zn are considerable. Fusion–evaporation is taken into account using the computational code of the NRV knowledge base. The results of calculations are in satisfactory agreement with the experimental data.  相似文献   

20.
We summarize recent experiments on thermal counterflow turbulence in superfluid 4He, emphasizing the observation of turbulence in the normal fluid and its effect on the decay process when the heat flux is turned off. We argue that what is observed as turbulence in the normal fluid is a novel form of coupled turbulence in the superfluid and normal components, with injection of energy on the scales of both the (large) channel width and the (small) spacing between quantized vortices. Although an understanding of this coupled turbulence remains challenging, a theory of its decay is developed which accounts for the experimental observations.  相似文献   

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