Normal 3He Research Articles

Observation of quantum limit of zero sound absorption in normal 3He at 400 MHz

We are studying the quantum limit of zero sound absorption in normal 3He in which sound quanta are absorbed or emitted directly by quasiparticles. For that experiment, high frequency ultrasound is required since the condition ℏ;ω ≥ κT must be satisfied. We have succeeded in observing zero sound at the frequency of 400 MHz which is high enough to confirm the quantum effect. In the preliminary experiment, the absorption decreases with the square of temperature as it predicted by Fermi liquid theory and is seen to remain finite at absolute zero temperature.

Viscosity anomaly of normal and superfluid 3He

We derived the viscosity and the slip length of normal and superfluid 3He by using a torsional oscillator with no adjustable parameter. We report the bulk shear viscosity of normal liquid 3He deviates from the T -2 dependence near the superfluid transition and the slip length of superfluid 3He must be enhanced.

Faraday effect for transverse waves in superfluid 3He-B

Low-frequency ( ω ≪ Δ(T)) transverse sound in superfluid 3He becomes overdamped at temperatures near T c . However, at low temperatures ( T≲0.3 T c ) the off-resonant coupling to the J=2 - , M=±1 modes stabilizes a propagating transverse current mode with a large phase velocity and low damping for frequencies above that of the J=2 - mode. A magnetic field with→ H|→ qlifts the degeneracy of right- and left-circularly polarized waves giving rise to the analog of circular dichroism and birefringence of electromagnetic waves. These features suggest that transverse waves may be more easily detected in the B-phase than in normal 3He. Below we give a brief summary of results on transverse waves in 3He-B [1].

Deep inelastic neutron scattering and momentum distributions in quantum liquids

A new method for extracting single particle properties and final state effects in quantum liquids and solids from neutron scattering data at high momentum transfer is presented. Using the method, the momentum distribution in normal 4He is found to differ significantly from a Gaussian. In superfluid 4He a condensate n 0=0.10±0.03 at T=1.42K is determined consistent with previous values. Applications to other systems are discussed.

Transverse waves in superfluid3He-B

We examine the theory of collisionless transverse current waves in bulk superfluid 3He-B, including the coupling to the order parameter collective modes. A t low frequencies, co << A(T), the order parameter modes do not contribute to the restoring force for a transverse current, and the quasiparticle contribution drops rapidly as the gap in the spectrum develops. Thus, low-frequency transverse sound becomes overdamped at temperatures near To. However, at low temperatures (T<0.3Tc) the off-resonant coupling to the J=2-, M=+I modes stabilizes a propagating transverse current mode, with a large phase velocity and low damping for frequencies above a critical frequency that is approximately that of the J = 2- mode. We also discuss the similarities and differences of longitudinal and transverse sound in the superfluid phases. For example, in zero field, right- and left-circularly polarized waves are degenerate. A magnet&field, with H II ~1, lifts this degeneracy, giving rise to the analog of circular dichroism and birefringence of electromagnetic waves. Thus, transverse waves may be more easily detected in the B-phase than in normal 3He.

Many-body theories of condensed phases of 4He and normal 3He

An introduction is given to the microscopic theories of liquid and solid 4He and of 3He in the normal liquid phase. The emphasis is on the variational theory of the ground state and of the excited states of the system. The role of two body, three body and higher order correlations is discussed also in relation to the recently introduced shadow wave function.

Anomalous magnetic relaxation in normal 3He at low temperatures

We have measured longitudinal magnetic relaxation at low temperatures in a bulk cell with walls made of Stycast 1266 epoxy. The results show no dependence on the magnetic field and unusual temperature behavior. The suggested explanation, if true, makes Stycast 1266 a plausible substrate for study of two-dimensional ferromagnetism in3He.

Slip of normal 3he on smooth surfaces

Abstract Measurements of the slip length of normal 3He confined by smooth silicon suggest that the boundary condition for 3He scattering at surfaces is diffuse even for substrates which are smooth compared to the mean thermal wavelength of 3He. Coating the surface with just two or three monolayers of 4He greatly increases the specularity. In addition, the expected behavior of the bulk viscosity of 3He appears to be modified by the reduced momentum transfer caused by the smooth surface and specular scattering condition.

Slip of normal 3He on smooth surfaces

Measurements of the slip length of normal 3He confined by smooth silicon suggest that the boundary condition for 3He scattering at surfaces is diffuse even for substrates which are smooth compared to the mean thermal wavelength of 3He. Coating the surface with just two or three monolayers of 4He greatly increases the specularity. In addition, the expected behavior of the bulk viscosity of 3He appears to be modified by the reduced momentum transfer caused by the smooth surface and specular scattering condition.

Surface coupling to collective and single-particle spin modes in normal 3He

The authors propose a simple technique for probing the single-particle and collective excitations in normal /sup 3/He via a standing magnetic surface wave of arbitrary /omega/ and fixed k generated by a meander-line coil. An analytic treatment of the Landau-Sillin equation enables them to calculate the power absorption spectrum, which displays singularities associated with the 1 = 0 spin mode and a Doppler-shifted spin resonance (DSSR) of the single-particle excitations. Experimental measurement of the spectrum would determine the Landau parameters (F/sub 0//sup a/, F/sub 1//sup a/) with a spectroscopic precision. Furthermore, observation of the DSSR thresholds would provide an independent determination of the Fermi velocity v and F/sub 0//sup a/. Finally, a possibility of exciting higher, 1 /ge/ 1, spin modes is briefly mentioned in the framework of an extended Leggett-Rice equation.

Effective interactions, elementary excitations, and transport in the helium liquids

Polarization potentials, the self-consistent fields that describe the primary consequences of the strong atom–atom interaction in the helium liquids, are developed for liquid 4He and 3He. Emphasis is placed on the common physical origin of the effective interactions in all helium liquids, and the hierarchy of physical effects (very short-range atomic correlations, zero-point motion, and the Pauli principle) that determine their strength is reviewed. An overview is then given of the application of polarization potential theory to experiment, including the phonon–maxon–roton spectra of 4He and 3He–4He mixtures, the phonon–maxon spectrum of normal and spin-polarized 3He, and the transport properties of superfluid 4He and of normal and spin-polarized 3He.

Surface Coupling to Collective and Single-Particle Spin Modes in Normal 3He

A simple technique is proposed for probing the single-particle and collective excitations in normal 3He via a standing magnetic surface wave of arbitrary ω and fixed k generated by a meander-line coil. The analytically calculated power absorption spectrum for 3He displays singularities associated with the l=0 spin mode and a Doppler-Shifted Spin Resonance of the single-particle excitations. Finally a possibility of exciting higer, l≥1, spin modes is discussed.

Transmission of Spin Waves through the Liquid 3He to 3He–4He Interface

We present a proposal for experiments to study the transmission of transverse spin waves across the interface between normal or superfluid 3He and saturated 3He-4He mixture. Our analysis is based on the general boundary condition for transverse magnetization formulated by Fredkin for ESR experiments on metal-to-metal junctions. Using a simple model, we find that the boundary coefficient for the liquid 3He-mixture interface is directly related to the quasiparticle transmission probability τ. The spin wave spectrum in a two-phase liquid sample between inert walls is calculated to show how τ might be measured.

Transverse Surface Impedance of Normal and Superfluid 3He

We present a variational calculation of the transverse surface impedance for normal and superfluid 3He which includes, through a microscopic boundary condition, a general class of boundary scattering laws for thermal excitations. Particularly, we study the consequences of specular, backward and (for superfluid 3He–B) Andreev scattering.

Quasihomogeneous Spin Waves with l=1 for Normal 3He in DC Magnetic Fields and Its Antiresonance

The dynamic spin susceptibility of the normal, degenerate and neutral Fermi liquid is found in the quasihomogeneous regime, with the accuracy ∼ (kR)2, at the collision integral taken in the ref. 1. The formula contains a spin wave pole with ℓ=1. This formula is used also to find the conditions when the ac magnetization term compensates the field H in the ac magnetic induction. The results are also valid for metals, if the vector k is directed along the dc magnetic field.

NMR in normal 3He using a meander-line coil.

A simple technique is proposed for probing the single-particle and collective excitations in a Fermi liquid via a standing magnetic surface wave of arbitrary $\ensuremath{\omega}$ and fixed $k$ generated by a meanderline coil. The calculated power absorption spectrum for $^{3}\mathrm{He}$ displays singularities associated with the $l=0$ spin-wave mode and a Doppler-shifted spin resonance of the single-particle excitations.

Reliable slip-on vacuum coupling for low-temperature apparatus

A reliable slip-on vacuum coupling scheme for low-temperature applications is described. The novel aspect of this concept is the use of silicone fluid as the sealing agent. The stem and coupling joint described has performed without failure at room temperature, immersed in normal 4He and in superfluid 4He.

Heat capacity of normal and superfluid 3He

The latest measurements of 3He heat capacity C in the normal Fermi liquid and below the superfluid transition temperature Tc are reviewed. Specifically, the consequences of the data by Alvesalo et al. are discussed in light of the latest experimental and theoretical results; this includes the temperature dependence of CT in the normal liquid, the effective mass of 3He, the anomalous behavior of CT near Tc below 8 bar, and strong coupling effects seen in the heat capacity of the superfluid phases.

Heat capacity of normal and superfluid 3He

The latest measurements of 3He heat capacity C in the normal Fermi liquid and below the superfiuid transition temperature T c are reviewed. Specifically, the consequences of the data by Alvesalo et al. are discussed in light of the latest experimental and theoretical results; this includes the temperature dependence of C T in the normal liquid, the effective mass of 3He, the anomalous behavior of C T near T c below 8 bar, and strong coupling effects seen in the heat capacity of the superfluid phases.

Vibrating wire experiments in 3HeB to 0.6 mK

Experiments with a vibrating wire in normal 3He and 3HeB have shown two effects that affect the interpretation of previous vibrating wire experiments: 1. (1) The presence of solid boundaries has a substantial effect on the phase of the response. 2. (2) Compressibility of the superfluid component is not negligible, especially near T c and at low pressures. In addition, we find evidence for finite mean free path effects at low temperatures and high pressures.