Propagating phonons in liquid 4He

Wyatt, A.F.G. and Lockerbie, N.A. and Sherlock, R.A. (1989) Propagating phonons in liquid 4He. Journal of Physics: Condensed Matter, 1 (22). pp. 3507-3522. ISSN 0953-8984 (http://dx.doi.org/10.1088/0953-8984/1/22/010)

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Abstract

at T approximately=0.1 K is studied as a function of pressure input power and propagation distance. Using a superconducting tunnel junction detector it is found that a single injected pulse can form two propagating pulses at low pressures but only one at high pressures. It is shown that three-phonon scattering can explain this behaviour. At low pressures, one group of phonons propagates ballistically while another group consists of strongly interacting phonons which travel at the ultrasonic velocity.