Collective modes in 2 dimensional fermionic superfluid near Pomeranchuk instability

In this work we investigate order parameter collective modes in 2 dimensional fermionic superfluids in finite angular momentum pairing channels. We discover subgap bosonic excitations with finite mass analogous to order parameter collective modes in 3 dimensional superfluid 3He. We further investigate the effect of fermion vacuum on these modes and it is shown that some of these modes in the spectrum soften as the underlying Fermi liquid approaches Pomeranchuk instability, or the nematic critical point when considering a p-wave chiral superfluid.