Comment on the coupling of zero sound to the J=1^- modes of³He-B

Features in the zero sound attenuation near the pair-breaking edge in superfluid³He-B have been observed in large magnetic fields. Schopohl and Tewordt [J. Low Temp. Phys.57, 601 (1984)] claim that the J=1^-, M=±1 order-parameter collective modes couple to zero sound as a result of the distortion of the equilibrium order parameter by a magnetic field; they identify the new features with these modes. However, we show that, when the effect of gap distortion on the collective modes is properly taken into account, the collective modes equations of Schopohl and Tewordt yield no direct coupling of zero sound to the J=1^- modes. Thus, the identification of the absorption features reported by Ling, Saunders, and Dobbs [Phys. Rev. Lett.59, 461 (1987)] near the pair-breaking edge with the J=1^- modes is not clearly established.