## CMT44

##
Parametric excitation of the J = 2^{+} modes by zero sound in superfluid ^{3}He-B

**Author(s):**
J. A. Sauls^{†} and R. H. McKenzie

**Comments:**
7 Journal pages

**Journal:**
Physica B: Condensed Matter, 169, 170-176 (1991)
[DOI]

**Abstract:**

We discuss order-parameter collective modes in weakly inhomogenous states of superfluid ^{3}He-B,
i.e., states in which the scale of the inhomogeneities is considerably longer than the coherence length,
ξ_{0} = ℏ v_{f} / 2π T_{c}, and the energy associated with the
inhomogeneity is small compared to the condensation energy. The theory describes resonance phenomena
between order-parameter modes and zero sound. We discuss two specific cases, both of which involve
excitation of the J = 2^{+} modes via a parametric field that lifts the selection rule due to
particle-hole symmetry. In the case of a static superflow the modes with
J = 2^{+}, M = ± 1 couple to sound for **q || H**, and should be observable
as Zeeman states with a maximum absorption that scales as the square of the superflow velocity.
The J = 2^{+} modes may also be excited parametrically in a three-wave resonance process
involving two zero-sound phonons. We summarize the nonlinear response theory for two-photon excitation
of these modes.

^{†}
Invited Paper for the Proceedings of the 19th International Conference on Low Temperature Physics,
Brighton, UK.

Paper:
[PDF]