New excitations in bcc ${}^4$He - an inelastic neutron scattering study

Abstract

We report neutron scattering measurements on bcc solid ${}^4$% He. We studied the phonon branches and the recently discovered ''optic-like'' branch along the main crystalline directions. In addition, we discovered another, dispersionless "optic-like'' branch at an energy around 1 meV ($\sim$~11K). The properties of the two "optic-like" branches seem different. Since one expects only 3 acoustic phonon branches in a monoatomic cubic crystal, these new branches must represent different type of excitations. One possible interpretation involves localized excitations unique to a quantum solid.

4 pages, 3 figures, accepted by PRB, Rapid Communications

Cited by in corpus (1)

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