Abstract:
The field dependence of the magnetic susceptibility and collective mode frequencies of superfluid
3He-B
are calculated perturbatively in
(γH/Δ)
using the quasiclassical theory. With the aid of this perturbation
theory, we interpret the gap distortion, nonlinear susceptibility, and collective excitations of the
order parameter in terms of additional correlations between Cooper pairs that are induced by a magnetic
field. We also calculate the dispersion splittings of the real squashing modes in a magnetic field.
In addition to the nonlinear Zeeman shifts of these modes, which occur in strong magnetic fields
(γH≈0.1Δ)
there are low-field
[γH≈(qvf)2/Δ]
nonlinearities of the collective mode frequencies resulting from the field dependence of the quantization
axis. Our results for all of these response properties of
3He-B
depend upon a small number of material parameters; thus measurements of these properties can provide
detailed information on the quasiparticle interactions.
Paper: [PDF]