Relaxation of anisotropic systems of quasi-particles in superfluid helium

• Published in: Journal of low temperature physics Vol. 145; no. 5-6; pp. 387 - 407
• Main Authors: ADAMENKO, I. N, NEMCHENKO, K. E, SLIPKO, V. A, WYATT, A. F. G
• Format: Journal Article
• Language: English
• Published: Heidelberg Springer 01-12-2006
• Subjects: Boson degeneracy and superfluidity of 4he; Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Physics; Quantum fluids and solids; liquid and solid helium; Superfluid helium 4; Momentum distribution; Quasiparticles; Relaxation; Rotons; Quasiparticle interactions; Anisotropy; Dispersion relations; Phonons; Superfluid; Angular distribution; Momentum density
• ISSN: 0022-2291; 1573-7357
• DOI: 10.1007/s10909-006-9250-4

We investigate the relaxation of boundless and anisotropic quasiparticle systems, in liquid He, with given initial values of momentum and energy densities. The evolution is governed by the dispersion curve which determines the interactions between quasi-particles. The first stage of the relaxation is the rapid creation of a quasistationary low-energy phonon system. This system transforms to another quasistationary system which contains high-energy phonons as well as low energy-phonons. Finally the system evolves to a stationary system of phonons and rotons. The temperature T and the drift velocity u are found for the closed quasi-particle system during its relaxation. This allows us to study the quasi-particle energy and the angular distribution of momentum, and the thermodynamic functions of the quasi-particles system, at each of stage of its evolution.