This work is motivated by recent experiments of V. V. Dmitriev's group, which investigated the effect of impurity magnetic scattering on the properties of the superfluid phases of ³He [1,2]. The experiments showed that the temperature range of the stable polar phase of superfluid ³He in a nematic aerogel vanishes when a small amount of solid paramagnetic ³He is present on the aerogel surface. In this case, a chiral polar-distorted A-phase with a finite degree of distortion emerges directly from the normal state instead of the axially symmetric polar phase.

We propose a microscopic mechanism for this instability based on the emergence of an effective spin-orbit interaction as quasiparticles scatter off the spatially inhomogeneous magnetic texture of the solid layer. Due to the finite curvature and roughness of the aerogel strands, a Berry curvature field is induced via magnetic correlations, lying primarily in the plane perpendicular to the anisotropy axis of aerogel. This interaction simultaneously breaks both the axial symmetry and the time-reversal invariance, which is essential for the observed effect.

Within Gorkov's equations in the p-wave channel, this double symmetry breaking introduces imaginary non-diagonal terms into the self-consistency matrix. Consequently, the pure polar phase no longer maximizes the transition temperature, yielding to the polar-distorted A-phase. In the limit where the interaction under consideration is strong enough, that is, when the non-diagonal elements of the perturbation matrix dominate over the difference between the diagonal ones, the solution approaches the form of the pure A-phase.

1. V. V. Dmitriev, A. A. Soldatov, A. N. Yudin, "Effect of Magnetic Boundary Conditions on Superfluid ³He in Nematic Aerogel", Phys. Rev. Lett., 120, 075301 (2018)
2. V. V. Dmitriev, D. V. Petrova, A. A. Soldatov, A. N. Yudin, “The effect of pressure on the splitting of the superfluid transition in ³He in nematic aerogel”, Pis’ma v ZhETF, 124,  216 (2026)
   
   
    

Evgeny Surovtsev
JETP Letters 124, issue 7 (2026)