Spin-polarized Fermi Liquids Research Articles

Transverse relaxation in two-level Fermi liquids and gases

An exact microscopic theory is developed for transverse dynamics in two-level Fermi systems like spin-polarized Fermi liquids. The origin of a transverse zero-temperature attenuation is a dephasing of interlevel transitions in inhomogeneous conditions. We analyze different sources of this relaxation using an extrapolation from low polarizations or densities. These sources include imaginary terms in the vertex and single-particles' energies and pseudo-energies away from the Fermi spheres, and derivatives of the vertex function in off-shell directions. The attenuation for dilute systems starts from a second order term in density. The main non-local contribution is of the next order in density, but is not negligible if the interaction range is large. At very low polarizations and densities, one recovers the already known results. The implications for liquid3He↑ and3He↑-4He mixtures are discussed.

Transverse spin dynamics in spin-polarized Fermi liquids

A microscopic framework for a generalized Landau theory is established in the form of two coupled equations in '~artial transverse densities". The 4-component effective interaction is related to the irreducible vertex, and not to the full vertex. The results explain the zero-temperature transverse relaxation and attenuation of spin waves. The spectrum of spin waves is expressed via harmonics of the interaction operator and its derivatives at arbitrary polarization. Our exact equations differ from previous semi-phenomenological ones, and reproduce all proper limiting cases like spin-polarized quantum gases or the Silin-Leggett low field equations.

Multiple spin echoes in spin polarized Fermi liquids

Multiple spin echoes (MSEs) in3He and in3He-4He mixtures have been analyzed using a theoretical technique proposed by Einzel et al. In both systems MSEs are generated by Fermi liquid interactions, but for3He, MSEs are also generated at higher temperatures by the dipolar demagnetizing field. The theory is compared with the experimental results for3He and with our measurements for3He-4He mixtures. We have improved on the fit to the second echo heights for3He given by Einzel et al. by taking account of both the Leggett-Rice effect and the dipolar interaction in the calculation. Good fits were also found for the first and second echo heights for the3He-4He data. The third echo height is larger than expected if we assume that the total magnetization remains uniform in space. We have developed the theory for the case when this approximation is not made, and we find good agreement for the first five echoes.

Conductivity in a spin-polarized band near the metal-insulator critical point

Millikelvin conductivity measurements of semimagnetic n-Cd 0.95Mn 0.5Se and p-Hg 0.915Mn 0.085Te in the region of the insulator-to-metal transition induced by the magnetic field are presented. The results of CdMnSe can be quantitatively explained on both sides of the transition by Finkelstein's renormalization group equations suitable for a spin-polarized Fermi liquid. The temperature dependence of the variable-range hopping conductivity in p-HgMnTe is consistent with the presence of a Coulomb anomaly at the Fermi level.

Pressure diffusion and sound absorption in spin-polarized quantum systems

Pressure diffusion and related phenomena are studied in the cases of Fermi liquids and dilute gases with arbitary degree of quantum degeneracy. An equation is derived expressing the (spin) pressure diffusion ratio through partial viscosities of (spin) components of systems. The exact values of corresponding transport coefficients are given for the cases of spin-polarized Boltzmann or degenerate quantum gases and spin-polarized Fermi liquids. The influence of surface slip effects on diffusion properties of spin-polarized quantum systems is discussed. The results may be used for gaseous and liquid3He,3He ↑ -4He solutions, gases H ↑ and D ↑, and other spin-polarized or binary quantum systems.