High-Resolution Study of Excitations in SuperfluidHe4by the Neutron Spin-Echo Technique

Abstract

Neutron scattering studies of elementary excitations can now, for the first time, be extended to the microelectronvolts resolution range by the use of the newly developed neutron spin-echo method. The first such experiment is described, and its results are shown to complement substantially previous knowledge on the temperature dependence of the energy and lifetime of the roton excitation, and the suggested onset of three-phonon decay beyond the roton minimum in superfluid ${}_{}{}^4{}_{}{}^{}\mathrm{He}$.