Phonons in magnon superfluid and symmetry breaking field

TL;DR

This paper discusses the spectrum of Goldstone modes in superfluid magnon liquids, highlighting how symmetry-breaking RF magnetic fields induce mass in phonons, with implications for understanding magnon Bose-Einstein condensation.

Contribution

It introduces a novel interpretation of coherent spin precession in 3He-B as magnon Bose-Einstein condensation and analyzes the phonon spectrum under symmetry-breaking fields.

Findings

RF magnetic field induces mass in phonon spectrum

Goldstone mode spectrum analyzed in superfluid magnon liquids

Experimental results support the Bose-Einstein condensation interpretation

Abstract

Recent experiments [1],[2] which measured the spectrum of the Goldstone collective mode of coherently precessing state in 3He-B are discussed using the presentation of the coherent spin precession in terms of the Bose-Einstein condensation of magnons. The mass in the spectrum of the Goldstone boson -- phonon in the superfluid magnon liquid -- is induced by the symmetry breaking field, which is played by the RF magnetic field