Incipient Pair-Fluctuation Corrections to Quasiparticle Transport in Liquid ³He

Nonequilibrium properties of a Fermi liquid are well described by a Boltzmann-Landau kinetic equation for the quasiparticle distribution function. For such a system at temperatures near the superfluid/superconductor phase transition, Cooper pair fluctuations are long-lived and can influence physical properties of the normal phase. We report new results for the leading corrections to the Landau kinetic equation using the Keldysh method that result from quasiparticle emission and absorption of long-lived pair fluctuations. As an application of our theory we calculate the increase in the attenuation of zero sound attenuation that results from the scattering of quasiparticles by long-lived pair fluctuations. The theoretical results are in excellent agreement with both the temperature and pressure dependence of the excess attenuation of zero sound reported by Paulson and Wheatley [1]. We also predict a correction to the zero sound velocity which should be observable.

Funding Acknowledgement: Research supported by NSF Grant DMR-1508730

[1] Paulson and Wheatley, Phys. Rev. Lett. 41, 561 (1978).