Physical review. B, Condensed matter
Fivefold splitting of the squashing collective mode of superfluid B3 by a magnetic field
Roman Movshovich, Eric Varoquaux, N. Kim, D. M. Lee
Abstract
We have conducted an ultrasonic pulse-time-of-flight investigation of the squashing mode of superfluid $^{3}\mathit{B}$ in a magnetic field. All five of the expected Zeeman sublevels for this J=${2}^{\mathrm{\ensuremath{-}}}$ mode were observed. The investigation was done at a very low temperature (T/${\mathit{T}}_{\mathit{c}}$0.35) to reduce the quasiparticle broadening that tends to smear the collective modes and makes resolution of the individual sublevels impossible. Variation of the pressure was used to sweep the collective-mode frequencies through the operating frequency, 137.6 MHz of the resonant-sound transducers. Both group-velocity spectroscopy and pulse-shape analysis were used for identification of different sublevels. Performing experiments at different orientations of the sound propagation with respect to magnetic-field direction (parallel, perpendicular, 55\ifmmode^\circ\else\textdegree\fi{}, and 13\ifmmode^\circ\else\textdegree\fi{}) was the key to observation of all five modes and their identification. The Land\'e g factor was obtained from the linear dependence of the ${\mathit{J}}_{\mathit{z}}$=+2 sublevel on magnetic field and compared with theory.